Prime root of n-th nontrivial prime power (A025475, A246547).

Terms

a(0) =2a(1) =2a(2) =3a(3) =2a(4) =5a(5) =3a(6) =2a(7) =7a(8) =2a(9) =3a(10) =11a(11) =5a(12) =2a(13) =13a(14) =3a(15) =2a(16) =17a(17) =7a(18) =19a(19) =2a(20) =23a(21) =5a(22) =3a(23) =29a(24) =31a(25) =2a(26) =11a(27) =37a(28) =41a(29) =43