A165681 Primes p such that 3*p*(p-1)+1 is not prime.

13, 17, 19, 23, 37, 41, 47, 61, 71, 73, 79, 83, 97, 101, 103, 107, 113, 127, 131, 139, 149, 151, 163, 167, 179, 181, 191, 193, 199, 211, 223, 227, 229, 233, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 317, 331, 337, 349, 359, 367, 373, 379, 383, 397, 401

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Formula

A000040 \ A165682.

a(n) ~ n log n. - Charles R Greathouse IV, Feb 23 2017

Mathematica

Select[Prime[Range[90]], !PrimeQ[3#(#-1)+1]&]  (* Harvey P. Dale, Mar 18 2011 *)

Prog

(PARI) is(n)=isprime(n) && !isprime(3*n*(n-1)+1) \\ Charles R Greathouse IV, Feb 23 2017

Crossrefs

Cf. A165682, A165683.

Sequence in context: A286042 A168447 A191059 * A214033 A268593 A175873

Adjacent sequences: A165678 A165679 A165680 * A165682 A165683 A165684

Keyword

nonn,easy

Author

Vincenzo Librandi, Sep 24 2009

Extensions

2 and 3 removed by R. J. Mathar, Sep 26 2009

Status

approved