Smallest prime p such that (n^p + (n+1)^p)/(2n+1) is prime, or -1 if no such p exists.

Terms

a(0) =3a(1) =3a(2) =3a(3) =5a(4) =3a(5) =3a(6) =7a(7) =3a(8) =7a(9) =53a(10) =47a(11) =3a(12) =7a(13) =3a(14) =3a(15) =41a(16) =3a(17) =5a(18) =11a(19) =3a(20) =3a(21) =11a(22) =11a(23) =3a(24) =5a(25) =103a(26) =3a(27) =37a(28) =17a(29) =7