A197038 Numbers k such that (2^k + 3^k)/97 is prime.

12, 412, 436, 916

Offset

1,1

Links

Table of n, a(n) for n=1..4.

Example

a(1) = 12 => (2^12+3^12)/97 = 5521 is prime ;
(2^a(2)+3^a(2))/97 has 195 digits ;
(2^a(3)+3^a(3))/97 has 207 digits ;
(2^a(4)+3^a(4))/97 has 436 digits ;

Mathematica

lst={}; Do[If[PrimeQ[(2^k+3^k)/97], AppendTo[lst, k]], {k, 1000}]; lst
Select[Range[10000], PrimeQ[(2^#+3^#)/97]&] (* Harvey P. Dale, Aug 22 2013 *)

Prog

(PARI) is(n)=ispseudoprime((2^n+3^n)/97) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A181628, A181636.

Sequence in context: A003772 A211078 A299382 * A282883 A163971 A340306

Adjacent sequences: A197035 A197036 A197037 * A197039 A197040 A197041

Keyword

nonn,hard

Author

Michel Lagneau, Oct 08 2011

Status

approved