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.

A023291 Primes that remain prime through 3 iterations of function f(x) = 8x + 1.

Original entry on oeis.org

2, 1487, 2207, 2927, 8807, 11117, 16187, 17657, 26357, 44927, 45377, 48497, 91757, 110237, 117167, 122327, 125387, 126107, 145007, 170927, 174527, 190787, 193847, 203897, 230567, 244247, 246017, 270287, 280547, 283937, 347957, 362237, 364337
Offset: 1

Views

Author

Keywords

Comments

Primes p such that 8*p+1, 64*p+9 and 512*p+73 are also primes. - Vincenzo Librandi, Aug 04 2010

Crossrefs

Subsequence of A005123, A023228, and A023260.

Programs

  • Magma
    [n: n in [1..450000] | IsPrime(n) and IsPrime(8*n+1) and IsPrime(64*n+9) and IsPrime(512*n+73)]; // Vincenzo Librandi, Aug 04 2010
  • Mathematica
    okQ[n_]:=And@@PrimeQ[NestList[8#+1&,n,3]]; Select[Prime[Range[50000]],okQ] (* Harvey P. Dale, Jan 09 2011 *)

Formula

a(n) == 17 (mod 30) for n > 1. - John Cerkan, Sep 23 2016