A249446 Numbers n such that 2*(n^2-1) - 1 and 2*(n^2-1) + 1 are primes.

2, 4, 10, 11, 34, 41, 46, 49, 56, 59, 76, 85, 95, 125, 160, 181, 185, 196, 200, 206, 220, 245, 266, 280, 295, 301, 304, 346, 365, 379, 386, 391, 440, 470, 505, 556, 571, 595, 659, 679, 689, 731, 784, 815, 820, 854, 869, 896, 944, 959, 994, 1001, 1004, 1015, 1025, 1154, 1250, 1345, 1376

Offset: 1

Author

Juri-Stepan Gerasimov, Oct 29 2014

Keywords

• nonn

Comments

Subsequence of A066049. - Michel Marcus, Oct 29 2014

n such that 2*n^2 - 2 is in A014574. - Robert Israel, Nov 18 2014

Examples

			2 is in this sequence because 2*(2^2-1) - 1 = 5 and 2*(2^2-1) + 1 = 7 are both prime.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..1600

Crossrefs

Cf. A001097, A014574, A066049, A066436, A201712.

Programs

Magma

[ n: n in [1..1400] | IsPrime(2*(n^2-1)-1) and IsPrime(2*(n^2-1)+1) ];

Maple

select(n -> isprime(2*n^2-3) and isprime(2*n^2-1), [$1 .. 10000]); # Robert Israel, Nov 18 2014

Mathematica

Select[Range[0, 1500], PrimeQ[2 #^2 - 3] && PrimeQ[2 #^2 - 1] &] (* Vincenzo Librandi, Oct 29 2014 *)

PARI

isok(n) = isprime(2*(n^2-1) - 1) && isprime(2*(n^2-1) + 1); \\ Michel Marcus, Oct 31 2014