Primes of the form 2^k+3^(k-1).

Terms

a(0) =3a(1) =7a(2) =17a(3) =43a(4) =113a(5) =307a(6) =857a(7) =20707a(8) =181243a(9) =539633a(10) =14414443a(11) =129402307a(12) =31389448217