a(n)= least k such that n^k*(n^k-1)-1 is prime with n > 1.

Terms

a(0) =2a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =3a(7) =1a(8) =1a(9) =1a(10) =1a(11) =10a(12) =1a(13) =5a(14) =1a(15) =1a(16) =2a(17) =2a(18) =1a(19) =1a(20) =1a(21) =2a(22) =4a(23) =1a(24) =4a(25) =1a(26) =12a(27) =1a(28) =328a(29) =1