Numbers k such that k prefixed by '3' and followed by '1' is prime.

Terms

a(0) =1a(1) =3a(2) =12a(3) =18a(4) =19a(5) =22a(6) =25a(7) =27a(8) =30a(9) =33a(10) =36a(11) =37a(12) =39a(13) =46a(14) =49a(15) =51a(16) =54a(17) =57a(18) =58a(19) =63a(20) =67a(21) =69a(22) =70a(23) =76a(24) =82a(25) =85a(26) =88a(27) =91a(28) =93a(29) =105