Largest prime factor of 3^(2n+1) - 1.

Terms

a(0) =2a(1) =13a(2) =11a(3) =1093a(4) =757a(5) =3851a(6) =797161a(7) =4561a(8) =34511a(9) =363889a(10) =368089a(11) =1001523179a(12) =391151a(13) =8209a(14) =20381027a(15) =4404047a(16) =2413941289a(17) =2664097031a(18) =17189128703a(19) =797161a(20) =86950696619a(22) =927001a(23) =96656723a(24) =131713a(25) =99810171997