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

12, 412, 436, 916

Offset: 1

Author

Michel Lagneau, Oct 08 2011

Keywords

• nonn
• hard
• more

Comments

a(5) > 10^5. - Michael S. Branicky, Apr 15 2025

Examples

			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.
		

Crossrefs

Cf. A181628, A181636.

Programs

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 *)

PARI

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