Numbers k such that k prefixed by '5' and followed by '1' is prime.

Terms

a(0) =2a(1) =4a(2) =7a(3) =10a(4) =17a(5) =23a(6) =26a(7) =28a(8) =35a(9) =38a(10) =43a(11) =44a(12) =47a(13) =50a(14) =52a(15) =53a(16) =58a(17) =59a(18) =64a(19) =65a(20) =70a(21) =71a(22) =74a(23) =79a(24) =80a(25) =82a(26) =85a(27) =86a(28) =88a(29) =98