Smallest prime factor of 2^n - 1 having the form k*n + 1.

Terms

a(0) =3a(1) =7a(2) =5a(3) =31a(4) =7a(5) =127a(6) =17a(7) =73a(8) =11a(9) =23a(10) =13a(11) =8191a(12) =43a(13) =31a(14) =17a(15) =131071a(16) =19a(17) =524287a(18) =41a(19) =127a(20) =23a(21) =47a(22) =241a(23) =601a(24) =2731a(25) =262657a(26) =29a(27) =233a(28) =31a(29) =2147483647