A023309 Primes that remain prime through 4 iterations of function f(x) = 3x + 8.

3181, 9551, 22051, 30941, 32621, 61981, 76651, 99961, 134291, 151901, 163661, 185951, 226691, 227671, 240551, 288191, 342821, 374501, 394411, 402881, 423781, 426301, 446461, 456151, 459091, 460951, 554011, 572321, 577601, 617191, 653831

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Primes p such that 3*p+8, 9*p+32, 27*p+104 and 81*p+320 are also primes. - Vincenzo Librandi, Aug 04 2010

Links

• John Cerkan, Table of n, a(n) for n = 1..10000

Crossrefs

Subsequence of A023210, A023248, and A023279.

Programs

Magma

[n: n in [1..1000000] | IsPrime(n) and IsPrime(3*n+8) and IsPrime(9*n+32) and IsPrime(27*n+104) and IsPrime(81*n+320)]; // Vincenzo Librandi, Aug 04 2010

Mathematica

okQ[n_]:=And@@PrimeQ/@Rest[NestList[3#+8&,n,4]]; Select[Prime[Range[60000]],okQ] (* Harvey P. Dale, Aug 16 2010 *)

Formula

a(n) == 1 or 31 (mod 70). - John Cerkan, Oct 04 2016