A023279 Primes that remain prime through 3 iterations of function f(x) = 3x + 8.

11, 31, 211, 1151, 3181, 5051, 5261, 6101, 6661, 9391, 9551, 10501, 11701, 13171, 15901, 16481, 19531, 22051, 24181, 26261, 27031, 28351, 28591, 28661, 29411, 30941, 31321, 32621, 38011, 40471, 42101, 48371, 49921, 57571, 59791, 61981, 66161, 67271

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

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

Links

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

Crossrefs

Subsequence of A023210 and of A023248.

Programs

Magma

[n: n in [1..150000] | IsPrime(n) and IsPrime(3*n+8) and IsPrime(9*n+32) and IsPrime(27*n+104)] // Vincenzo Librandi, Aug 04 2010

Mathematica

Select[Prime@ Range@ 7000, Times @@ Boole@ PrimeQ@ Rest@ NestList[3 # + 8 &, #, 3] > 0 &] (* Michael De Vlieger, Sep 19 2016 *)

PARI

is(n)=isprime(n) && isprime(3*n+8) && isprime(9*n+32) && isprime(27*n+104) \\ Charles R Greathouse IV, Sep 20 2016

Formula

a(n) == 1 (mod 10). - John Cerkan, Sep 16 2016