Numbers k such that k concatenated with k+4 is a prime.

Terms

a(0) =3a(1) =5a(2) =17a(3) =27a(4) =35a(5) =39a(6) =45a(7) =47a(8) =63a(9) =65a(10) =83a(11) =93a(12) =99a(13) =113a(14) =123a(15) =147a(16) =149a(17) =173a(18) =185a(19) =203a(20) =209a(21) =213a(22) =219a(23) =227a(24) =239a(25) =249a(26) =255a(27) =263a(28) =267a(29) =285