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

1,1

Comments

Subsequence of A066049. - Michel Marcus, Oct 29 2014

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

Links

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

Example

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

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 *)

Prog

(Magma) [ n: n in [1..1400] | IsPrime(2*(n^2-1)-1) and IsPrime(2*(n^2-1)+1) ];
(PARI) isok(n) = isprime(2*(n^2-1) - 1) && isprime(2*(n^2-1) + 1); \\ Michel Marcus, Oct 31 2014

Crossrefs

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

Sequence in context: A029984 A101519 A227204 * A184815 A290473 A356664

Adjacent sequences: A249443 A249444 A249445 * A249447 A249448 A249449

Keyword

nonn

Author

Juri-Stepan Gerasimov, Oct 29 2014

Status

approved