Numbers k such that k prefixed by '4' and followed by '7' is prime.

Terms

a(0) =5a(1) =6a(2) =8a(3) =12a(4) =15a(5) =17a(6) =21a(7) =29a(8) =32a(9) =33a(10) =35a(11) =39a(12) =44a(13) =45a(14) =50a(15) =51a(16) =54a(17) =56a(18) =59a(19) =63a(20) =65a(21) =78a(22) =81a(23) =87a(24) =93a(25) =95a(26) =96a(27) =98a(28) =101a(29) =104