%N Numbers k such that 3^k + 3*k + 1 is prime.
%o (PARI) is(n)=ispseudoprime(3^n+3*n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Numbers k such that b^k + b*k + 1 is prime: A301634 (b=2), this sequence (b=3), A301635 (b=5).
%Y Cf. A176805, A180269.
%A _N. J. A. Sloane_, Sep 04 2010, based on a posting to the Sequence Fans Mailing List by _Charles R Greathouse IV_, Aug 23 2010
%E More terms from _Charles R Greathouse IV_, Sep 07 2010