a(n) is the smallest k > 2^n such that 2^(k-1) == 1 (mod (2^n-1)*k).

Terms

a(0) =3a(1) =5a(2) =13a(3) =17a(4) =41a(5) =67a(6) =197a(7) =257a(8) =523a(9) =1031a(10) =2069a(11) =4129a(12) =8243a(13) =16451a(14) =32911a(15) =65537a(16) =131479a(17) =262153a(18) =524591a(19) =1048601a(20) =2097229a(21) =4194389a(22) =8388791a(23) =16777441a(24) =33554501a(25) =67108913a(26) =134217757a(27) =268435889a(28) =536871259a(29) =1073741971