Largest prime factor of 7^n + 1.

Terms

a(0) =2a(1) =2a(2) =5a(3) =43a(4) =1201a(5) =191a(6) =181a(7) =911a(8) =169553a(9) =117307a(10) =4021a(11) =10746341a(12) =1201a(13) =228511817a(14) =13564461457a(15) =6568801a(16) =47072139617a(18) =13841169553a(19) =4058036683a(20) =810221830361a(21) =309079a(22) =83960385389