Largest prime factor of 3^n + 1.

Terms

a(0) =2a(1) =2a(2) =5a(3) =7a(4) =41a(5) =61a(6) =73a(7) =547a(8) =193a(9) =37a(10) =1181a(11) =661a(12) =6481a(13) =398581a(14) =16493a(15) =271a(16) =21523361a(17) =1021a(18) =530713a(19) =101917a(20) =42521761a(21) =2269a(22) =570461a(23) =23535794707a(24) =769a(25) =22996651a(26) =4795973261a(27) =19927a(28) =647753a(29) =5385997