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A152912 Primes p such that 2*p^2-1 is not prime. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified February 25 13:47 EST 2021. Contains 341609 sequences. (Running on oeis4.)