A152912 Primes p such that 2*p^2-1 is not prime.

5, 19, 23, 29, 31, 37, 47, 53, 61, 67, 71, 79, 83, 89, 97, 101, 103, 107, 131, 139, 149, 151, 163, 167, 173, 191, 193, 223, 227, 229, 233, 239, 241, 257, 269, 271, 281, 283, 307, 313, 317, 331, 337, 347, 349, 359, 373, 383, 389, 397, 401, 421, 431, 439, 443

Offset

1,1

Comments

Primes not in A106483. Primes p such that 2p^2-1 is not in A092057. - R. J. Mathar, Dec 19 2008

Links

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

Maple

a := proc (n) if isprime(n) = true and isprime(2*n^2-1) = false then n else end if end proc: seq(a(n), n = 1 .. 500); # Emeric Deutsch, Jan 02 2009

Mathematica

Select[Prime[Range[100]], !PrimeQ[2 #^2 - 1] &] (* Vincenzo Librandi, Aug 30 2012 *)

Prog

(Magma) [p: p in PrimesUpTo(500)|not IsPrime(2*p^2-1)]; // Vincenzo Librandi, Aug 30 2012

Crossrefs

Cf. A092057, A106483, A007588.

Sequence in context: A275954 A087840 A074229 * A191054 A097934 A191609

Adjacent sequences: A152909 A152910 A152911 * A152913 A152914 A152915

Keyword

nonn,easy

Author

Vincenzo Librandi, Dec 15 2008

Extensions

Definition clarified by R. J. Mathar, Dec 19 2008

Extended by Emeric Deutsch, Jan 02 2009

Status

approved