Prime nearest to 2^n. In case of a tie, choose the smaller.

Terms

a(0) =2a(1) =2a(2) =3a(3) =7a(4) =17a(5) =31a(6) =61a(7) =127a(8) =257a(9) =509a(10) =1021a(11) =2053a(12) =4093a(13) =8191a(14) =16381a(15) =32771a(16) =65537a(17) =131071a(18) =262147a(19) =524287a(20) =1048573a(21) =2097143a(22) =4194301a(23) =8388617a(24) =16777213a(25) =33554467a(26) =67108859a(27) =134217757a(28) =268435459a(29) =536870909