a(0)=1; for n > 0, a(n) = next prime after 2^(n-1).

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =11a(5) =17a(6) =37a(7) =67a(8) =131a(9) =257a(10) =521a(11) =1031a(12) =2053a(13) =4099a(14) =8209a(15) =16411a(16) =32771a(17) =65537a(18) =131101a(19) =262147a(20) =524309a(21) =1048583a(22) =2097169a(23) =4194319a(24) =8388617a(25) =16777259a(26) =33554467a(27) =67108879a(28) =134217757a(29) =268435459