cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-8 of 8 results.

A007350 Where the prime race 4k-1 vs. 4k+1 changes leader.

Original entry on oeis.org

3, 26861, 26879, 616841, 617039, 617269, 617471, 617521, 617587, 617689, 617723, 622813, 623387, 623401, 623851, 623933, 624031, 624097, 624191, 624241, 624259, 626929, 626963, 627353, 627391, 627449, 627511, 627733, 627919, 628013, 628427, 628937, 629371
Offset: 1

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Author

Keywords

Comments

The following references include some on the "prime race" question that are not necessarily related to this particular sequence. - N. J. A. Sloane, May 22 2006
Starting from a(12502) = A051025(27556) = 9103362505801, the sequence includes the 8th sign-changing zone predicted by C. Bays et al. The sequence with the first 8 sign-changing zones contains 194367 terms (see a-file) with a(194367) = 9543313015387 as its last term. - Sergei D. Shchebetov, Oct 13 2017

References

  • Ford, Kevin; Konyagin, Sergei; Chebyshev's conjecture and the prime number race. IV International Conference "Modern Problems of Number Theory and its Applications": Current Problems, Part II (Russian) (Tula, 2001), 67-91.
  • Granville, Andrew; Martin, Greg; Prime number races. (Spanish) With appendices by Giuliana Davidoff and Michael Guy. Gac. R. Soc. Mat. Esp. 8 (2005), no. 1, 197-240.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A156749 [sequence showing Chebyshev bias in prime races (mod 4)]. - Daniel Forgues, Mar 26 2009

Programs

  • Mathematica
    lim = 10^5; k1 = 0; k3 = 0; t = Table[{p = Prime[k], If[Mod[p, 4] == 1, ++k1, k1], If[Mod[p, 4] == 3, ++k3, k3]}, {k, 2, lim}]; A007350 = {3}; Do[ If[t[[k-1, 2]] < t[[k-1, 3]] && t[[k, 2]] == t[[k, 3]] && t[[k+1, 2]] > t[[k+1, 3]] || t[[k-1, 2]] > t[[k-1, 3]] && t[[k, 2]] == t[[k, 3]] && t[[k+1, 2]] < t[[k+1, 3]], AppendTo[A007350, t[[k+1, 1]]]], {k, 2, Length[t]-1}]; A007350 (* Jean-François Alcover, Sep 07 2011 *)
    lim = 10^5; k1 = 0; k3 = 0; p = 2; t = {}; parity = Mod[p, 4]; Do[p = NextPrime[p]; If[Mod[p, 4] == 1, k1++, k3++]; If[(k1 - k3)*(parity - Mod[p, 4]) > 0, AppendTo[t, p]; parity = Mod[p, 4]], {lim}]; t (* T. D. Noe, Sep 07 2011 *)

A007352 Where the prime race 3k-1 vs. 3k+1 changes leader.

Original entry on oeis.org

2, 608981813029, 608981813507, 608981813683, 608981813819, 608981814127, 608981814143, 608981818999, 608981820977, 608981826877, 608981826977, 608981827873, 608981828201, 608981836363, 608981836493, 608981836681, 608981836973, 608981836993, 608981837063
Offset: 1

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Comments

Terms a(2n+1) form a subsequence of A098044.

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence, although the terms are incorrect - see A185703).

Crossrefs

Extensions

Terms from a(3) onwards corrected by Max Alekseyev, Feb 10 2011

A297408 Where the prime race among 10k+1, ..., 10k+9 changes leader.

Original entry on oeis.org

2, 13, 157, 193, 347, 383, 587, 673, 907, 1163, 1327, 1483, 1907, 1933, 2897, 4723, 5557, 5573, 6037, 6113, 6637, 6673, 7487, 8273, 8317, 8363, 8387, 8443, 8467, 8573, 8647, 8803, 8837, 8933, 9277, 9293, 10067, 10103, 11897, 11923, 12037, 12073, 12107, 12143
Offset: 1

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Author

Sean A. Irvine, Dec 29 2017

Keywords

Comments

A007355 appears to be an erroneous version of this sequence.

Crossrefs

Programs

  • PARI
    a297408(limit)={my(v=vector(10),vm=0,ivm=0,imv); forprime(p=2,limit,my(m=p%10);v[m]++;my(mv=vecmax(v,&imv));if(mv>vm,if(imv!=ivm,print1(p,", "); ivm=imv);vm=mv))};
    a297408(12500) \\ Hugo Pfoertner, Jul 25 2021
    
  • Python
    from sympy import nextprime
    from itertools import islice
    def agen():
        c, p, leader = [0 for i in range(10)], 1, None
        while True:
            p = nextprime(p); last = p%10; c[last] += 1; m = max(c)
            if c.count(m) == 1 and c.index(m) == last and last != leader:
                yield p; leader = last
    print(list(islice(agen(), 44))) # Michael S. Branicky, Dec 20 2022

A007353 Where the prime race among 5k+1, ..., 5k+4 changes leader.

Original entry on oeis.org

2, 83, 137, 293, 337, 443, 487, 523, 557, 743, 797, 1213, 1277, 1523, 1657, 1733, 1867, 1973, 2027, 2063, 2797, 2833, 2887, 4733, 5227, 5323, 5437, 5503, 5527, 5623, 5897, 5923, 6007, 6133, 6317, 6353, 6427, 6563, 6607, 6703, 7187, 7283, 7307, 7393, 7477, 8963
Offset: 1

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Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

A007354 Where the prime race among 7k+1, ..., 7k+6 changes leader.

Original entry on oeis.org

2, 17, 131, 227, 733, 829, 929, 997, 1097, 1123, 1237, 1277, 1447, 1487, 1531, 1627, 1811, 1907, 1993, 2141, 2203, 2267, 2441, 2677, 2707, 3209, 3299, 3433, 3547, 3853, 4003, 4021, 4507, 4679, 4787, 4931, 5081, 5113, 7537, 7577, 7649, 7759, 7817, 8039, 8461, 8543
Offset: 1

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Author

Keywords

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • PARI
    primerace(mod,limit)={my(v=vector(mod), vm=0, ivm=0, imv); forprime(p=2, limit, my(m=p%mod); v[m+1]++;  v[m+1]++; my(mv=vecmax(v, &imv)); if(mv>vm, if(imv!=ivm, print1(p, ", "); ivm=imv); vm=mv))};
    primerace(7,8600) \\ Hugo Pfoertner, Jul 25 2021

A297407 Where the prime race among 9k+1, ..., 9k+8 changes leader.

Original entry on oeis.org

2, 167, 191, 419, 461, 563, 587, 617, 677, 761, 857, 881, 929, 1427, 1451, 1607, 1667, 1777, 1823, 1867, 1913, 2351, 2399, 2459, 4127, 4583, 5039, 5087, 5171, 7283, 7349, 7517, 7547, 7643, 7691, 7901, 8681, 8837, 8933, 11243, 11903, 11927, 18329, 18371, 19913
Offset: 1

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Author

Sean A. Irvine, Dec 29 2017

Keywords

Crossrefs

Programs

  • Maple
    V:= <(0$8)>:
    lead:= 1:
    Res:= NULL:
    count:= 0:
    p:= 1:
    while count < 100 do
      p:= nextprime(p);
      t:= p mod 9;
      V[t]:= V[t]+1;
      if V[t] > V[lead] then
        lead:= t;
        Res:= Res, p;
        count:= count+1;
      fi
    od:
    Res; # Robert Israel, Jan 01 2018

A297410 Where the prime race among 11k+1, ..., 11k+10 changes leader.

Original entry on oeis.org

2, 73, 101, 149, 233, 359, 431, 509, 563, 1051, 1091, 1151, 1259, 1459, 1553, 1811, 2609, 2713, 2741, 4363, 4507, 4561, 4919, 5023, 5189, 6761, 7321, 7433, 7717, 7829, 8039, 8081, 8951, 9043, 9203, 9337, 9851, 9931, 10181, 10457, 11437, 11491, 13099, 19841
Offset: 1

Views

Author

Sean A. Irvine, Dec 29 2017

Keywords

Crossrefs

A297411 Where the prime race among 12k+1, ..., 12k+11 changes leader.

Original entry on oeis.org

2, 17, 79, 101, 163, 197, 211, 263, 281, 379, 401, 443, 461, 479, 631, 677, 739, 809, 907, 953, 1087, 1109, 1171, 1193, 1543, 1607, 1721, 1759, 2063, 2203, 2417, 2543, 2633, 2711, 2731, 2753, 3203, 3221, 3323, 3607, 3803, 3847, 3863, 3943, 4397
Offset: 1

Views

Author

Sean A. Irvine, Dec 29 2017

Keywords

Crossrefs

Showing 1-8 of 8 results.