Exactly 5 digits from {1,2,3,4,5,6,7,8,9} can precede a(n) to form a prime.

Terms

a(0) =1a(1) =7a(2) =9a(3) =39a(4) =63a(5) =77a(6) =83a(7) =221a(8) =229a(9) =237a(10) =521a(11) =547a(12) =689a(13) =719a(14) =733a(15) =741a(16) =803a(17) =861a(18) =907a(19) =1283a(20) =1647a(21) =2003a(22) =2051a(23) =2073a(24) =2467a(25) =2727a(26) =3003a(27) =3063a(28) =3331a(29) =3487