Numbers k such that (7^k + 1)/8 is a prime.

Terms

a(0) =3a(1) =17a(2) =23a(3) =29a(4) =47a(5) =61a(6) =1619a(7) =18251a(8) =106187a(9) =201653a(10) =1178033a(11) =1321757a(12) =1827773a(13) =3417779