A225098 - OEIS

%I #27 Aug 31 2020 02:40:17

%S 2,3,7,13,15,21,43,49,63,69,127,155,183,211,231,237,259,265,273,293,

%T 301,323,335,391,435,441,447,489,505,573,595,671,713,715,743,757,797,

%U 811,951,959,973,979,987,993,1035,1147,1197,1287,1359,1393,1415,1429,1443,1491,1525,1597,1617,1653

%N Numbers k such that k^2 - 2 and 2*k^2 - 1 are both prime.

%C Primes in the sequence: 2, 3, 7, 13, 43, 127, 211, 293, 743, 757, 797, 811, 1429,...

%H Amiram Eldar, <a href="/A225098/b225098.txt">Table of n, a(n) for n = 1..10000</a>

%e 2^2 - 2 = 2 is prime and 2*2^2 - 1 = 7 is prime, so a(1) = 2.

%t Select[Range[1653], PrimeQ[#^2 - 2] && PrimeQ[2*#^2 - 1] &] (* _T. D. Noe_, May 10 2013 *)

%Y Intersection of A028870 and A066049.

%K nonn

%O 1,1

%A _Gerasimov Sergey_, Apr 27 2013

%E Corrected by _R. J. Mathar_, May 05 2013