A181636 - OEIS

%I #6 Mar 30 2012 18:35:54

%S 61,4621,369181,2414250301,1282861452271981,103911691734684541,

%T 102329189594547549657540565413396038701,

%U 28900785585664327723593061693364968422740414514061,7915715496579381803076374342089862963295414837600820914397695027296168074652778681081092369443226449741

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

%C 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 , ...}.

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

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

%e   prime.

%p with(numtheory):for n from 1 to 350 do: x:= (2^n + 3^n)/13:if floor(x)=x and

%p   type(x,prime)=true then printf(`%d, `, x):else fi:od:

%Y Cf. A181628

%K nonn

%O 1,1

%A _Michel Lagneau_, Nov 18 2010