Main site of science textbooks
Crowdfunding site for the free
online science textbooks project

Number theory: A survey of computational obstacles and results
Jason Maron

Diophantine equations

A Diophantine equation has integer coefficients and integer exponents, and integer solutions are studied. The number of terms is finite.

A1 X1N1 + A2 X2N2 + A3 X3N3 + ... = 0

A transcendental Diophantine equation is any equation for which integer solutions are studied.

Arrows show corollaries.


Equation                 Theorems and conjectures

A * B = C                Prime numbers. Twin prime conjecture, Prime gaps, Prime clusters

A + B = C                Goldbach conjecture
                         Mason-Strothers conjecture  ->  ABC conjecture
                         Baker conjecture            ->  ABC conjecture  ->  Mordell theorem
                                                                         ->  Fermat theorem
                                                                         ->  General Pilai conjecture

AX + BY = C              Generalized Eliot-Halberstam conjecture  ->  Eliot-Halberstam conjecture
                         Polignac conjecture  ->  Twin prime conjecture
                         Goldbach conjecture

X1N + X2N + ... + XTN = 0 Ekl conjecture, Euler's sum-of-powers counterexamples
                         Langlands reciprocity conjecture  ->  Modularity theorem  ->  Fermat theorem
                                                           ->  Birch & Swinnerton-Dyer conjecture
                         Geometric Langlands conjecture

AX + BY = CZ              ABC  ->  Fermat-Catalan conj  ->  Beal conj  ->  Generalized Fermat theorem  ->  Fermat theorem

Prime gaps               Generalized Riemann Hypothesis  ->  Riemann hypothesis
                         Cramer conjecture        ->  Brocard conjecture  ->  Legende conjecture
                         Oppermann conjecture     ->  Brocard conjecture  ->  Legende conjecture
                         Oppermann conjecture     ->  General Andrica conjecture  ->  Andrica conjecture
                         Firoozbakht conjecture   ->  Cramer upper bound
                         FGKMT lower bound
                         Bateman-Horn conjecture  ->  First Hardy-Littlewood conjecture
                         Gilbreath conjecture

X1 + X2 + ... + XN = 0   Strong n conjecture  ->  n conjecture  ->  ABC conjecture

M/N = X-1 + Y-1 + Z-1     Generalized Erdos-Straus conjecture  ->  Erdos-Straus conjecture for M=4

A XM - B YN = C          Pillai conjecture  ->  Hall conjecture

2N + 1 = P + 2Q          Lamoine conjecture  ->  Goldbach weak conjecture

2N + 1 = P + M(M+1)      Sun conjecture

X2 + Y2 <= R2            Generalized Gauss circle problem  ->  Gauss circle problem

N! + 1 = M2            Brocard problem

XY - YX                  ABC conjecture  ->  Weak Hall conjecture

Plane set, rational dist Bombieri-Lang conjecture ->  Erdos-Ulam false
                         ABC conjecture           ->  Erdos-Ulam false

                         Schinzel hypothesis H  ->  Dickson conjecture       ->  Twin prime conjecture
                                                                             ->  Sophie Germain conjecture

Prime gaps

The maximal gap function Gap(X) is the size of the biggest prime gap up to prime X.

A "record" gap at X is such that there are no known gaps of larger magnitude at smaller X. It doesn't necessarily mean that they don't exist. In the chart, all known record gaps are shown.

Some primality tests are guaranteed to correctly distinguish between a prime and composite. Some tests are probabilistic. They have good accuracy but occassionally a composite passes the test. Such a composite is called a "pseudoprime".

In the chart, "guaranteed gaps" are record gaps with guaranteed primes. "Probable gaps" are record gaps with probable primes.

The average gap size at X scales as ln(X). The scaling for the maximal gap is poorly constrained, as is the gap distribution.

If gap size G is Gaussian distributed as e-(G/lnX)2, the maximal gap scales as Gap(X) ~ ln3/2X.

If gaps are exponentially distributed as e-G/lnX, the maximal gap scales as Gap(X) ~ ln2X. This is the Cramer conjecture.

Numerical evidence supports an exponential distribution but there is a computational limit for how far we can explore the tail. The limit hinges on sieve size and memory.

                                  Gap(X)

Upper bound, proven, 1852         X                                          Assumes a prime between P and 2P.  Bertrand postulate
Upper bound, proven, 1930         X32999/33000                                 Hoheisel
Upper bound, proven, ?            X249/250                                     Heilbronn
Upper bound, proven, 1936         X3/4                                        Cudakov
Upper bound, proven, 1937         X5/8                                        Ingram       Implies a prime between successive cubes
Upper bound, proven, 1972         X7/12                                       Huxley
Upper bound, proven, 2001         X.525                                       Baker, Harman, & Pintz
Upper bound, conjecture, 1912     X1/2                                        Legendre conj.  Assumes a prime between successive squares
Upper bound, conjecture, 1969     X1/2/ln(X)                                  Grimm conjecture
Upper bound, conjecture, 1936     ln(X) ln(X)                                 Cramer
Upper bound, conjecture, 1982     ln(x) ln(x) - ln(x) - 1                     Firoozbakht  Assumes PN1/N strictly decreasing, where PN is the Nth prime
Riemann hypothesis corollary 1936 X1/2 ln(X)                                  Cramer

Lower bound, proven, 1931         ln(X)                                       Westzynthius
Lower bound, proven, 1938         ln(X) lnln(X) lnlnlnln(X) / [lnlnln(X)]2    Rankin
Lower bound, proven, 2018         ln(X) lnln(X) lnlnlnln(X) /  lnlnln(X)      Ford-Green-Konyagin-Maynard-Tao

Ekl conjecture

Define an Ekl polynomial Ekl(N,U,V).

X1N + X2N + ... + XUN  =  Y1N + Y2N + ... + YVN

Q = U + V - N

The Ekl conjecture is that all integer solutions have Q>=0. The Fermat theorem follows.

Denote a solution with brarckets. For example, a solution for Ekl(2,1,2) is:

52 = 32 + 42      <-->     [5] = [3 4]

Euler's sum of powers conjecture

Euler's sum of powers conjecture is that Q>=1 for integer solutions of Ekl(N,1,V). It was proven false with counterexamples for N=4 and N=5. No counterexamples exist for N>5. The smallest counterexample for N=4 and N=5 is

4224814 = 958004 + 2175194 + 4145604
   1445 =    275 +     845 +    1105 + 1335

Solutions for Ekl(N,1,V) with Q=1 are known only for N = {2, 3, 4, 5, 7, 8}


First Hardy-Littlewood conjecture

The First Hardy-Littlewood conjecture (1923) is that the density of prime M-tuples at X is 1/lnM(X).

The prime number theorem is the case M=1 and was proven in 1896 by Hadamard & Poussin independently.

In 1915, Brun proved that the number of twin primes less than X is less than (2/3) X/lnM(X).

The Bateman-Horn conjecture (1962) generalizes the First Hardy-Littlewood conjecture.


Polignac conjecture

The Polignac conjecture (1849) is that there are infinitely many prime M-tubles for all M.

t was proved for M >= 70,000,000 by Zhang in 1013, and for M >= 246 by the Polymath8 project in 2014.

If the Eliot-Halberstam conjecture is true, then the Polignac conjecture is true for M >= 12. If the generalized Eliot-Halberstam conjecture is true, then the Polignac conjecture is true for M >= 6.


Beal conjecture

Generalized Fermat equation:

AX + BY = CZ

Beal conjecture: All integer solutions with {X, Y, Z} > 2, {A, B, C} have a common prime factor.

The Fermat-Catalan conjecture is that there are only finitely many solutions with A, B, and C being positive integers with no common prime factor and X, Y, and Z being positive integers satisfying X-1 + Y-1 + Z-1 < 1

The Beal conjecture can be restated as "All Fermat-Catalan conjecture solutions use 2 as an exponent".

The ABC conjecture implies that there are at most finitely many counterexamples to the Beal conjecture.


Fermat theorem

Proofs for specific exponents:

      Exponent

             3   1770   Euler
             4   1670   Fermat
             5   1825   Legendre; Dirichlet
             6   1802   Kausler
             7   1869   Lame
            10   1913   Kapferer
            14   1832   Dirichlet
          <270   1823   Germain
         <2522   1954   Vandiver       Computer proof
       <125000   1978   Wagstaff       Computer proof
      <4000000   1993                  Computer proof
          Even   1977   Terjanian
 Regular prime          Kummer         Conjecture: 61% of primes are regular
           All   1995   Wiles

                 1955   Modularity conjecture.  Taniyama & Shimura
                 1983   Falting theorem
                 1984   Frey theorem
                 1986   Ribet theorem
                 2001   Modularity theorem

Catalan conjecture

The Catalan conjecture was posed in 1842: The only solution to AX - BY = 1 is 32 - 23 = 1. It was proved in 2002 by Mihailescu.


Riemann zeros

To find zeros of the Riemann Zeta function, use the Hardy Z function, which is real-valued function along the critical line.

Search for sign changes. Use root-finding (Newton, Brent, secant, etc.). Count how many zeros were found. Independently count how many zeros should exist using the Riemann-von Mangoldt formula. If the counts agree, every zero up to that height lies on the critical line. This is the method used in essentially every large-scale verification.

The Odlyzko-Schonhage formula evaluates all zeros in an interval collectively, at a cost of ln(X) per zero.

The density of zeros is ln(X)

For evaluating the Hardy function at a single point, the Riemann-Siegel formula scales as X½.

Calculations use interval arithmetic, ball arithmetic, and arbitrary precision libraries. Each computed value is an interval guaranteed to contain the true value. Packages like Arb (now integrated into FLINT) make this practical.

The Riemann hypothesis is equivalent to all Li coefficients being positive, although this test is more expensive than evaluating zeros.


Hardy Z function

The scaling for RMS magnitude is H(X) = ln(X)

The scaling for moments of order m is [ln X]m2/4 Keating-Snaith random matrix prediction


Euler polynomials

To search for solutions to Euler polynomials Elk(N,1,N) up to height H, the naive computational scaling is N HN / (N-1)!.

Meet-in-the-middle technique improves the scaling to N H(N-1)/2.

Modular sieving can reduce the search space and reduce the constant in front of the scaling.


Andrica conjecture

The generalized Andrica conjecture is PN+1Z - PNZ < 1 if Z < .670873.... where PN+1 is the Nth prime.

The Andrica conjecture is for the case Z=1/2.


Legendre conjecture

There are at least 1 primes between successive squares. This implies that there are at least 2 primes between successive prime squares.


Brocard conjecture

There are at least 4 primes between successive prime squares. The Brocard conjecture implies th Legendre conjecture.


Primality tests

Some tests are guaranteed to correctly distinguish between a prime and composite. Some tests are probabilistic. They have good accuracy, but occassionally a composite passes the test. Such a composite is called a "pseudoprime".

                                                    Scaling

Baillie-PSW                            Probable
Adleman-Pomerance-Rumely                            [ln X]ln ln ln X
Agrawal-Kayal-Saxena                   Guarantee    [ln X]6        2002
Agrawal-Kayal-Saxena + Agarwal conj.   Guarantee    [ln X]3        2005

Baillie-PSW primality test

The Baillie–PSW primality test is a probabilistic or possibly deterministic primality testing algorithm that determines whether a number is composite or is a probable prime. It is named after Robert Baillie, Carl Pomerance, John Selfridge, and Samuel Wagstaff.

The Baillie–PSW test is a combination of a strong Fermat probable prime test to base 2 and a standard or strong Lucas probable prime test. The Fermat and Lucas test each have their own list of pseudoprimes, that is, composite numbers that pass the test. There is no known overlap between these lists, and there is even evidence that the numbers tend to be of different kind, in fact even with standard and not strong Lucas test there is no known overlap.

Computers show that there no Baille-PSW pseudoprimes below 1.9e18.


Montgomery pair correlation conjecture

The conjecture is that zeros of the Riemann zeta function have a correlation function of

1 - [(sin(π X) / (π X)]2

The conjecture has big numerical support.


Big numbers

Let X have B bits. The cost of integer multiplication is M(B) = B2. FFT techniques can sometimes reduce this to M(B) = B log2B.

                             Digits          X    Reach scaling

Reach, Riemann zeros             12       4e11    M(B) X ln(X)
Reach, Euler cuboid              13        e12    M(B) X3
Reach, Erdos-Straus conjecture   18        e17    M(B) X
Reach, Goldbach conjecture       19       4e18    M(B) X ln ln X
Reach, ABC conjecture            20        e19
Reach, Firoozbakht conjecture    19       4e18
Reach, prime number sieve        20        e19    M(B) X ln ln(X)         Memory is X½
Reach, prime gap, maximal        20        e19
Reach, prime gap, proven          7    1113106
Reach, prime gap, probable        8   16045848
Reach, Collatz conjecture        20        e20    X
Reach, Ekl(6,1,5)                       730000    X5/2
Reach, Ekl(6,1,6)                                 X3
Reach, Ekl(7,1,5)                                 X5/2
Reach, Ekl(8,1,7)
Reach, Ekl(9,1,8)
Reach, Ekl(9,1,9)
Reach, Ekl(7,3,4)
Reach, Ekl(9,4,5)
Reach, Ekl(10,5,5)
Reach, Li coefficient
Reach, Catalan-Beal conj.
Reach, Aliquot sequence
Reach, Agrawal conjecture        18        e17
Reach, Andrica conjecture        20       2e19
Reach, Hall conjecture           29       6e28
Reach, Lamoine conjecture        11       1e10
Reach, Gilbreath conjecture      20     1.5e15
Reach, Brocard problem           16       1e16    Known solutions are (4,5), (5,11), (7,71)

Biggest Mersenne prime     41000000        Big
Biggest probable prime      8200000        Big     M(B) ln(B)            Miller-Rabin PRP test
Biggest twin prime           388342        Big
Biggest triplet prime         20008        Big
Biggest Riemann zero             35       8e34     M(B) X½

Skewes point, proven            317   1.49e316
Skewes point, min               175    1.5e174
Skewes point, prime pair          7    1369391    Wolf 2011
Skewes point, prime triple        6     337867    Toth 2019
Skewes point, prime 4-tuple       7    1172531    Toth 2019
Skewes point, prime 5-tuple       8   21432401    Toth 2019
Skewes point, prime 6-tuple      12               Toth 2019                   251331775687
Skewes point, prime 7-tuple      13               Pfoertner 2020             7572964186421
Skewes point, prime 8-tuple      16               Pfoertner & Luhn 2020   1203255673037261
Mertens lower bound              17        e16
Mertens upper bound          8.5e18        Big
Polya conj min counterexample     9  906150257    Tanaka 1980

Archimedes sand reckoner #       63        Big
Googol                          100        Big
Googolplex                    10100        Big

Integer,  4 byte                 10        2e9
Integer,  8 byte                 19       9e18
Integer, 16 byte                 39       2e38
Integer, 32 byte                 77       6e76
Float,    4 byte                 39       3e38
Float,    8 byte                309      2e308
Float,   16 byte               4933     1e4932

Near-collisions involving small integers

  1    =  32 - 23
 24    =  210- 103
 13    =  28 - 35
  3    =  27 - 53
  2    =  33 - 52
104    =  36 - 54
  1    =  23 - 7
  4    =  53 - 112
  7    =  27 - 112
7153   =  312- 219

  1    =  2*5 - 32
  5    =  53 - 3*23
  1    =  24 - 3*5
  2    =  25 - 2*3*5
  5    =  7*15 - 102
  1.75 ~  (3/2)12 - 27         Pythagorean comma. Relates musical octaves to fifths.
  1.024=  27/53  =  210/103
7/5    ~  2½
 Pi    ~ 22/7
e^P    ~ 20
e^e    ~ 15.15

Clusters:

 7,  8,  9, 10
25, 27, 30, 32

Ekl conjecture

The tables gives minimum value of Q known from numerical examples, along with the minimal example. Solutions for Ekl(N,1,2) are ruled out by the Fermat theorem.

  N   U   V   Q

  2   1   2   1   [5]     = [3  4]                  Pythagorean triples           Antiquity
  3   1   3   1   [6]     = [3 4 5]                                               Antiquity
  4   1   3   0   [422481]= [95800 217519 414560]   Euler counterexample    1998  Elkies
  5   1   4   0   [144]   = [27 84 110 133]         Euler counterexample    1967  Lander et al.
  6   1   7   2   [1141]  = [76 234 402 474 702 894 1077]                   1967  Lander et al.
  7   1   7   1   [568]   = [525 439 430 413 266 258 127]                   1999  Dodrill
  8   1   8   1   [1409]  = [1324 1190 1088 748 524 478 223 90]                   Chase; Meyrignac   Only solution known
  9   1  10   2   [917]   = [851 822 668 625 574 542 475 179 99 42]
 10   1  13   4   [228]   = [210 204 187 179 128 122 85 73 59 57 49 13 6]         Chase

  2   2   2   2   [2 11]     = [5 10]                                             Antiquity
  3   2   2   1   [1 12]     = [9 10]                                             Antiquity
  4   2   2   0   [59 158]   = [133 134]                                    1772  Euler
  5   2   3   0   [141325 2205] = [140685 62375 50275]                      1997  Scher & Seidl
  6   2   5   1   [770 1117] = [84 212 602 861 1092]                        1999  Brisse
  7   2   6   1   [125 24]   = [121 94 83 61 57 27]                               Meyrignac
  8   2   7   1   [1303 1127]= [1334 976 648 623 516 401 272]                     Chase; Meyrignac   Only solution known
  9   2   9   2   [137 69]   = [121 116 116 115 89 52 28 26 14 9]           2002  Wroblewski
 10   2  12   4   [112 99]   = [109 103 89 79 72 59 59 52 20 15 5 5]        2000  Pliousnine 2000, 2000 Kuosa

  5   3   3   1   [3 54 62]  = [24 28 67]                                   1967  Lander et al.
  6   3   3   0   [3 19 22]  = [10 15 23]                                   1934  Subba Rao
  7   3   5   1   [96 41 17] = [87 77 77 68 56]
  8   3   5   0   [966 539 81]=[954 725 481 310 158]                        2003  Chase, Meyrignac, Resta & Meyrignac
  9   3   9   3   [38 38 3]  = [41 23 20 20 18 13 13 12 9]                  1998  Ekl
 10   3  11   4   Solutions known                                           2002  Wroblewski

  6   4   4   2   [2 2 9 9]            = [3 5 6 10]                         1934  Rao
  7   4   4   1   [149 123 14 10]      = [146 129 90 15]                    1996  Ekl
  8   4   4   0   [3113 2012 1953 861] = [2823 2767 2557 1128]              2006  Kuosa
  9   4   6   1   [90 64 35 35]        = [86 80 62 43 27 16]
 10   4   9   3   Solutions known                                           2002  Wroblewski

  9   5   5   1   [192 101 91 30 26]   = [180 175 116 17 12]                1997  Ekl
 10   5  16  11   Solutions known

 10   6   6   2   [95 71 32 28 25 16]  = [92 85 34 34 23 5]                 2002  Kuosa

In the table, the first column is N and the top row is U. The interior is the minimum known Q for integer solutions of Ekl(N,U,V) with U <= V.

      U ->  1   2   3   4   5   6
  N
  2         1   2
  3         1   1
  4         0   0
  5         0   0   1
  6         2   1   0   2
  7         1   1   1   1
  8         1   1   0   0
  9         2   2   3?  1   1
 10         4   4   4   3   7?  2

Tetration

Tetration can represent numbers from 0 to eeeeee on the same scale. It goes beyond a logarithmic scale.

Define "tetration":

Tet(0) = 1
Tet(1) = e
Tet(2) = ee
Tet(3) = eee

Tet(Q+1) = eTet(Q)

Define a continuous function Tet(Q)=X. It has an analytic form that is complicated to express. We use a piecewise interpolation with unit intervals.

-1 < Q < 0       0 < X < 1        X = Q+1         Q = -1 +          X
 0 < Q < 1       1 < X < e        X = eQ          Q =  0 +       ln(X)
 1 < Q < 2       e < X < ee       X = ee(Q-1)       Q =  1 +    ln ln(X)
 2 < Q < 3       ee< X < eee      X = eee(Q-2)       Q =  2 + ln ln ln(X)
etc.

Dyson swarm computer

Supercomputers today have a speed of 1018 Flop/second. A computer powered by a blue giant star has a speed of order 1048 Flop/second. A computer powered by a galaxy cluster has a speed of order 1056 Flop/second.

Speed, computer in 2026       =    e18  Flop/second
Speed, blue giant computer    =    e48  Flop/second
Speed, galaxy cluster computer=    e56  Flop/second

Power, blue giant star        =    e32  Watt
Power, large galaxy           =    e36  Watt
Power, galaxy cluster         =    e40  Watt

Energy per Flop, 2026         =  1e-12  Joule/Flop
Energy per flop, far future   =  1e-16  Joule/Flop

Lifetime, calculation of today=   3e7   second    =    1 year
Lifetime, blue giant star     =   3e13  second    =   10 million years
Lifetime, galaxy cluster      =   3e17  second    =   10 billion years

Computer Flop total, 2026          =   3e25  Flop
Computer Flop total, blue giant    =   3e61  Flop
Computer Flop total, galaxy cluster=   3e73  Flop

Cosmic numbers

                                                  Years

Summer and winter switch                          13000
Supervolcano timescale, 1 km3                     17000
Supervolcano timescale, 1000 km3                 100000
Supervolcano timescale, 3000 km3                 500000
Asteroid timescale, 1 km                          1 mil
The African rift becomes an ocean                10 mil
Lifetime of a blue giant star                    10 mil
Atlantic ocean volcano ring forms                20 mil
San Andreas fault moves LA and SF together       50 mil
Asteroid timescale, 10 km                       100 mil
Atlantic changes from expand to contract        125 mil
Sun orbit time around Galaxy                    240 mil
Supercontinent forms                            250 mil
Pacific Ocean stops expanding                   350 mil
Plate tectonics stop                            650 mil
Oceans evaporate. Moon outspiral stops         1100 mil
Mars becomes warm enough for liquid water      1550 mil
Sun nova                                       7590 mil
Milky Way and Andromeda merge                    10 bil
Big Rip, minimum time                            22 bil
Galaxies outside the LG are gone                125 bil
Local Group galaxies merge                      300 bil
Universe gravitationally segments               325 bil
Red dwarf lifetime                              15 tril
Star formation ends                            100 tril
Proton decay                                        e43
Black hole evap, 1 solar mass                       e67
Biggest supermassive black holes evaporate         e109
Vacuum collapse                                    e161
Inflationary event from tunneling           10^10^10^56

Links

Euler polynomials
Euler polynomials. Mathworld
Prime gap list
Euler polynomials
Big primes. t5.org
Encyclopedia of integer sequences
Prime gaps
Prime gaps


References
"Extreme Value Theory Analysis of Prime Gap Distributions: Statistical Analysis of Cram'er's Conjecture and Light-Tailed Behavior". G. Afriyie 2025

https://www.tandfonline.com/doi/full/10.1080/0025570X.2025.2481010#abstract Prime gaps
Ekl, R. L. "Equal Sums of Four Seventh Powers." Math. Comput. 65, 1755-1756, 1996.
Ekl, R. L. "New Results in Equal Sums of Like Powers." Math. Comput. 67, 1309-1315, 1998.
Elkies, N. "On A^4+B^4+C^4=D^4." Math. Comput. 51, 828-838, 1988.
Hoffman, P. The Man Who Loved Only Numbers: The Story of Paul Erdős and the Search for Mathematical Truth. New York: Hyperion, p. 195, 1998.
Lander, L. J. and Parkin, T. R. "A Counterexample to Euler's Sum of Powers Conjecture." Math. Comput. 21, 101-103, 1967.
Lander, L. J.; Parkin, T. R.; and Selfridge, J. L. "A Survey of Equal Sums of Like Powers." Math. Comput. 21, 446-459, 1967
Letac, A. Gazetta Mathematica 48, 68-69, 1942.
Meyrignac, J.-C. "Computing Minimal Equal Sums of Like Powers." http://euler.free.fr.
Moessner, A. "Einige Numerische Identitaten." Proc. Indian Acad. Sci. Sect. A 10, 296-306, 1939.
Subba Rao, K. "On Sums of Sixth Powers." J. London Math. Soc. 9, 172-173, 1934.
Wiles 1994
E. Brisse 1999
Resta 1999
Resta and Meyrignac 2003
1934 Subba Rao
M. Dodrill 1999, PowerSum
Erik Westzynthius Largest known zero of the Riemann zeta function https://mathoverflow.net/questions/264052/largest-known-zero-of-the-riemann-zeta-function


Acknowledgements

Acknowledgments: The author thanks ChatGPT (OpenAI) for discussions that helped organize ideas, clarify terminology, and explore possible frameworks for presenting computational reach in mathematics.


Main page

Support the free online science textbooks project






© Jason Maron, all rights reserved.

Data from Wikipedia unless otherwise specified.