%I #4 Feb 25 2024 00:11:06
%S 1,5,7,1003,40513
%N Numbers k such that (6^k + 6*k)/6 is prime.
%C If it exists, a(6) > 62000.
%o (PARI) is(n) = ispseudoprime(6^(n-1)+n)
%Y Cf. A058828, A221908, A226200.
%K nonn,hard,more
%O 1,2
%A _Hugo Pfoertner_, Feb 24 2024