Largest prime factor of 9^n - 7^n.
2, 2, 193, 13, 21121, 193, 1979713, 4481, 1279, 21121, 5520791, 4993, 26851943, 1979713, 795871, 84449, 60016610166713, 399043, 688344052841, 21121, 4439401, 5520791, 68063301125552099, 452857, 42922814046401, 26851943, 56941921, 181192427137
1
T. D. Noe, Plot of 100 terms
T. D. Noe, Table of 100 terms
Eric W. Weisstein, MathWorld: Greatest Prime Factor
(Mma) Table[FactorInteger[9^n - 7^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015