login
A173903
Numbers k such that both (2^k+1)^2-2 and (2^k-1)^2-2 are prime.
0
2, 3, 12, 15, 18, 21, 27
OFFSET
1,1
COMMENTS
a(8) > 9394. - Max Z. Scialabba, Jan 21 2024
a(8) > 695631 using A091513 and A091515. - Michael S. Branicky, Oct 24 2024
FORMULA
A091513 INTERSECT A091515. - R. J. Mathar, Jul 06 2010
MATHEMATICA
Select[Range[3000], PrimeQ[((2^# + 1)^2 - 2)]&&PrimeQ[((2^# - 1)^2 - 2)] &] (* Vincenzo Librandi, Aug 21 2014 *)
PROG
(Magma) [n: n in [1..400] | IsPrime((2^n-1)^2-2) and IsPrime((2^n+1)^2-2)]
CROSSREFS
Sequence in context: A302844 A180630 A173079 * A154785 A374730 A090512
KEYWORD
nonn,hard,more,changed
AUTHOR
Vincenzo Librandi, Mar 08 2010
EXTENSIONS
Definition clarified by Jon E. Schoenfield, Jun 18 2010
STATUS
approved