Primes reached in A037271, or -1 if no such prime exists.

Terms

a(0) =211a(1) =23a(3) =311a(4) =773a(5) =223a(6) =13367a(7) =1129a(8) =31636373a(9) =233a(11) =37a(12) =211a(13) =331319a(14) =773a(15) =3251a(16) =13367a(17) =227a(18) =547a(19) =241271a(20) =311a(21) =31397a(22) =1129a(23) =71129a(24) =373a(25) =313a(27) =379a(28) =22815088913a(29) =3411949a(30) =223