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%I #29 Oct 24 2024 14:55:05
%S 2,3,12,15,18,21,27
%N Numbers k such that both (2^k+1)^2-2 and (2^k-1)^2-2 are prime.
%C a(8) > 9394. - _Max Z. Scialabba_, Jan 21 2024
%C a(8) > 695631 using A091513 and A091515. - _Michael S. Branicky_, Oct 24 2024
%F A091513 INTERSECT A091515. - _R. J. Mathar_, Jul 06 2010
%t Select[Range[3000], PrimeQ[((2^# + 1)^2 - 2)]&&PrimeQ[((2^# - 1)^2 - 2)] &] (* _Vincenzo Librandi_, Aug 21 2014 *)
%o (Magma) [n: n in [1..400] | IsPrime((2^n-1)^2-2) and IsPrime((2^n+1)^2-2)]
%Y Cf. A091513, A091515.
%K nonn,hard,more
%O 1,1
%A _Vincenzo Librandi_, Mar 08 2010
%E Definition clarified by _Jon E. Schoenfield_, Jun 18 2010