A173903 Numbers k such that both (2^k+1)^2-2 and (2^k-1)^2-2 are prime.

2, 3, 12, 15, 18, 21, 27

Offset: 1

Author

Vincenzo Librandi, Mar 08 2010

Keywords

• nonn
• hard
• more
• changed

Comments

a(8) > 9394. - Max Z. Scialabba, Jan 21 2024

a(8) > 695631 using A091513 and A091515. - Michael S. Branicky, Oct 24 2024

Crossrefs

Cf. A091513, A091515.

Programs

Magma

[n: n in [1..400] | IsPrime((2^n-1)^2-2) and IsPrime((2^n+1)^2-2)];

Mathematica

Select[Range[3000], PrimeQ[((2^# + 1)^2 - 2)]&&PrimeQ[((2^# - 1)^2 - 2)] &] (* Vincenzo Librandi, Aug 21 2014 *)

Formula

A091513 INTERSECT A091515. - R. J. Mathar, Jul 06 2010

Extensions

Definition clarified by Jon E. Schoenfield, Jun 18 2010