OFFSET
1,1
COMMENTS
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
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