Primes of the form 2*3^k + 1.A111974Primes of the form 2*3^k + 1.Terms a(0) =3a(1) =7a(2) =19a(3) =163a(4) =487a(5) =1459a(6) =39367a(7) =86093443a(8) =258280327External referencesoeis: A111974