If b(n) = the largest proper divisor of n, then a(n) = (2^n - 1)/(2^b(n) - 1).

Terms

a(0) =3a(1) =7a(2) =5a(3) =31a(4) =9a(5) =127a(6) =17a(7) =73a(8) =33a(9) =2047a(10) =65a(11) =8191a(12) =129a(13) =1057a(14) =257a(15) =131071a(16) =513a(17) =524287a(18) =1025a(19) =16513a(20) =2049a(21) =8388607a(22) =4097a(23) =1082401a(24) =8193a(25) =262657a(26) =16385a(27) =536870911a(28) =32769a(29) =2147483647