A181628 -id:A181628 - cp's OEIS frontend

A181636 Primes of form (2^n + 3^n)/13.

61, 4621, 369181, 2414250301, 1282861452271981, 103911691734684541, 102329189594547549657540565413396038701, 28900785585664327723593061693364968422740414514061, 7915715496579381803076374342089862963295414837600820914397695027296168074652778681081092369443226449741

Offset: 1

Michel Lagneau, Nov 18 2010

nonn

Numbers n such that (2^n + 3^n)/13 is prime are listed in A181628 = {6, 10, 14, 22, 34, 38, 82, 106, 218, 334, 4414 , ...}.

			4621 is in the sequence because (2^10+ 3^10)/13 = 60073/13 = 4621 is
  prime.

Cf. A181628

with(numtheory):for n from 1 to 350 do: x:= (2^n + 3^n)/13:if floor(x)=x and
  type(x,prime)=true then printf(`%d, `, x):else fi:od:

a(n) = (2^A181628(n) + 3^A181628(n))/13.

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

Original entry on oeis.org

12, 412, 436, 916

Offset: 1

Michel Lagneau, Oct 08 2011

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

			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.

Cf. A181628, A181636.

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 *)

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

cp's OEIS Frontend

A181636 Primes of form (2^n + 3^n)/13.

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