Largest proper substring of n-th prime that is prime (0 if none).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =3a(6) =7a(7) =0a(8) =3a(9) =2a(10) =3a(11) =7a(12) =0a(13) =3a(14) =7a(15) =5a(16) =5a(17) =0a(18) =7a(19) =7a(20) =7a(21) =7a(22) =3a(23) =0a(24) =7a(25) =0a(26) =3a(27) =7a(28) =0a(29) =13