This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A152912 #17 Sep 05 2024 19:14:31 %S A152912 5,19,23,29,31,37,47,53,61,67,71,79,83,89,97,101,103,107,131,139,149, %T A152912 151,163,167,173,191,193,223,227,229,233,239,241,257,269,271,281,283, %U A152912 307,313,317,331,337,347,349,359,373,383,389,397,401,421,431,439,443 %N A152912 Primes p such that 2*p^2-1 is not prime. %C A152912 Primes not in A106483. Primes p such that 2p^2-1 is not in A092057. - _R. J. Mathar_, Dec 19 2008 %H A152912 Vincenzo Librandi, <a href="/A152912/b152912.txt">Table of n, a(n) for n = 1..1000</a> %p A152912 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 %t A152912 Select[Prime[Range[100]], !PrimeQ[2 #^2 - 1] &] (* _Vincenzo Librandi_, Aug 30 2012 *) %o A152912 (Magma) [p: p in PrimesUpTo(500)|not IsPrime(2*p^2-1)]; // _Vincenzo Librandi_, Aug 30 2012 %Y A152912 Cf. A092057, A106483, A007588. %K A152912 nonn,easy %O A152912 1,1 %A A152912 _Vincenzo Librandi_, Dec 15 2008 %E A152912 Definition clarified by _R. J. Mathar_, Dec 19 2008 %E A152912 Extended by _Emeric Deutsch_, Jan 02 2009