Smallest prime beginning and ending in 2n+1 or 0 if no such prime exists.

Terms

a(0) =11a(1) =3a(2) =5a(3) =7a(4) =919a(5) =11a(6) =13a(7) =0a(8) =17a(9) =19a(10) =21121a(11) =23a(12) =0a(13) =27127a(14) =29a(15) =31a(16) =33533a(17) =0a(18) =37a(19) =39139a(20) =41a(21) =43a(22) =0a(23) =47a(24) =49549a(25) =51151a(26) =53a(27) =0a(28) =57457a(29) =59