a(n) = (2^n - 1)/product(2^p - 1) where the product is over all distinct primes p that divide n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =5a(4) =1a(5) =3a(6) =1a(7) =85a(8) =73a(9) =11a(10) =1a(11) =195a(12) =1a(13) =43a(14) =151a(15) =21845a(16) =1a(17) =12483a(18) =1a(19) =11275a(20) =2359a(21) =683a(22) =1a(23) =798915a(24) =1082401a(25) =2731a(26) =19173961a(27) =704555a(28) =1a(29) =1649373