Largest prime factor of 2^n - 1.

Terms

a(0) =3a(1) =7a(2) =5a(3) =31a(4) =7a(5) =127a(6) =17a(7) =73a(8) =31a(9) =89a(10) =13a(11) =8191a(12) =127a(13) =151a(14) =257a(15) =131071a(16) =73a(17) =524287a(18) =41a(19) =337a(20) =683a(21) =178481a(22) =241a(23) =1801a(24) =8191a(25) =262657a(26) =127a(27) =2089a(28) =331a(29) =2147483647