Numbers k such that k prefixed by '6' and followed by '1' is prime.

Terms

a(0) =0a(1) =3a(2) =4a(3) =6a(4) =9a(5) =10a(6) =12a(7) =13a(8) =15a(9) =21a(10) =22a(11) =27a(12) =30a(13) =31a(14) =36a(15) =42a(16) =45a(17) =48a(18) =49a(19) =52a(20) =55a(21) =57a(22) =58a(23) =66a(24) =69a(25) =70a(26) =76a(27) =78a(28) =79a(29) =84