Digit '5' concatenated with a(n) is a prime.

Terms

a(0) =3a(1) =9a(2) =21a(3) =23a(4) =41a(5) =47a(6) =57a(7) =63a(8) =69a(9) =71a(10) =77a(11) =87a(12) =93a(13) =99a(14) =101a(15) =107a(16) =113a(17) =119a(18) =147a(19) =153a(20) =167a(21) =171a(22) =179a(23) =189a(24) =197a(25) =209a(26) =227a(27) =231a(28) =233a(29) =237