Least number k > (2n-1) such that (2n-1)^k - 2 is prime, or 0 if no such number exists.

Terms

a(0) =0a(1) =4a(2) =14a(3) =8a(4) =11a(5) =22420a(6) =78a(7) =17a(8) =24a(9) =20a(10) =25a(11) =24a(12) =63a(13) =30a(14) =42a(15) =69a(16) =128a(17) =50a(18) =119a(19) =204a(20) =2816a(21) =76a(22) =52a(23) =288a(24) =64a(25) =66a(26) =184a(27) =153a(28) =67a(29) =268