Smallest prime p such that 2+p^n is a prime, or 0 if no such prime exists.

Terms

a(0) =3a(1) =3a(2) =3a(3) =3a(4) =11a(5) =0a(6) =53a(7) =3a(8) =11a(9) =3a(10) =23a(11) =0a(12) =71a(13) =3a(14) =3a(15) =0a(16) =5a(17) =0a(18) =521a(19) =0a(20) =1847a(21) =0a(22) =41a(23) =3a(24) =71a(25) =3a(26) =59a(27) =0a(28) =191a(29) =0