a(n) = smallest prime of the form (2n-1)^k - 2, or 0 if no such number exists.

Terms

a(0) =0a(1) =7a(2) =3a(3) =5a(4) =7a(5) =14639a(6) =11a(7) =13a(8) =24137567a(9) =17a(10) =19a(12) =23a(13) =727a(14) =839a(15) =29a(16) =31a(17) =1223a(18) =1367a(19) =37a(20) =2825759a(21) =41a(22) =43a(23) =2207a(24) =47a(26) =7890479a(27) =53a(29) =12117359a(30) =59a(31) =61