Largest prime factor of 3^n - 1.

Terms

a(0) =2a(1) =2a(2) =13a(3) =5a(4) =11a(5) =13a(6) =1093a(7) =41a(8) =757a(9) =61a(10) =3851a(11) =73a(12) =797161a(13) =1093a(14) =4561a(15) =193a(16) =34511a(17) =757a(18) =363889a(19) =1181a(20) =368089a(21) =3851a(22) =1001523179a(23) =6481a(24) =391151a(25) =797161a(26) =8209a(27) =16493a(28) =20381027a(29) =4561