Numbers k such that k prefixed by '5' and followed by '7' is prime.

Terms

a(0) =4a(1) =5a(2) =7a(3) =8a(4) =10a(5) =14a(6) =16a(7) =19a(8) =22a(9) =23a(10) =29a(11) =34a(12) =38a(13) =40a(14) =41a(15) =43a(16) =47a(17) =50a(18) =52a(19) =55a(20) =64a(21) =65a(22) =71a(23) =73a(24) =80a(25) =82a(26) =85a(27) =86a(28) =89a(29) =92