Odd prime factors of generalized Fermat numbers of the form 5^(2^m) + 1 with m >= 0.

Terms

a(0) =3a(1) =13a(2) =17a(3) =257a(4) =313a(5) =641a(6) =769a(7) =2593a(8) =11489a(9) =19457a(10) =65537a(11) =163841a(12) =786433a(13) =1503233a(14) =1655809a(15) =7340033a(16) =14155777a(17) =18395137a(18) =23606273a(19) =29423041a(20) =39714817a(21) =75068993a(22) =167772161a(23) =2483027969a(24) =4643094529a(25) =6616514561a(26) =47148957697a(27) =241931001601