Concatenation of nextprime(a(n)) and a(n) is a prime.

Terms

a(0) =3a(1) =27a(2) =33a(3) =39a(4) =47a(5) =51a(6) =53a(7) =61a(8) =63a(9) =91a(10) =111a(11) =123a(12) =129a(13) =131a(14) =143a(15) =173a(16) =189a(17) =199a(18) =211a(19) =217a(20) =219a(21) =231a(22) =233a(23) =237a(24) =257a(25) =273a(26) =279a(27) =301a(28) =319a(29) =341