A249446 - OEIS

%I #22 Sep 08 2022 08:46:10

%S 2,4,10,11,34,41,46,49,56,59,76,85,95,125,160,181,185,196,200,206,220,

%T 245,266,280,295,301,304,346,365,379,386,391,440,470,505,556,571,595,

%U 659,679,689,731,784,815,820,854,869,896,944,959,994,1001,1004,1015,1025,1154,1250,1345,1376

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

%C Subsequence of A066049. - _Michel Marcus_, Oct 29 2014

%C n such that 2*n^2 - 2 is in A014574. - _Robert Israel_, Nov 18 2014

%H Colin Barker, <a href="/A249446/b249446.txt">Table of n, a(n) for n = 1..1600</a>

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

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

%t Select[Range[0, 1500], PrimeQ[2 #^2 - 3] && PrimeQ[2 #^2 - 1] &] (* _Vincenzo Librandi_, Oct 29 2014 *)

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

%o (PARI) isok(n) = isprime(2*(n^2-1) - 1) && isprime(2*(n^2-1) + 1); \\ _Michel Marcus_, Oct 31 2014

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

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Oct 29 2014