Largest prime factor of 9^n + 1.

Terms

a(0) =2a(1) =5a(2) =41a(3) =73a(4) =193a(5) =1181a(6) =6481a(7) =16493a(8) =21523361a(9) =530713a(10) =42521761a(11) =570461a(12) =769a(13) =4795973261a(14) =647753a(15) =47763361a(17) =1743831169a(18) =282429005041a(19) =25480398173a(20) =128653413121a(21) =109688713a(22) =56625998353a(24) =24127552321a(25) =61070817601