%I #7 Feb 29 2024 01:38:56
%S 1,3,7,15,3907
%N Numbers k such that (8^k + 8*k)/8 is prime.
%C If it exists, a(6) > 50000.
%o (PARI) is(n) = ispseudoprime(8^(n-1) + n)
%Y Cf. A221910, A226201.
%K nonn,hard,more
%O 1,2
%A _Hugo Pfoertner_, Feb 27 2024
