Largest prime factor of 7^n - 5^n.
2, 3, 109, 37, 6841, 109, 372709, 89, 127, 6841, 100057, 1801, 365146211, 372709, 102031, 31729, 75724224211, 30133, 1467606615817, 6841, 372709, 168846239, 181909325071, 4654801, 41682356332151, 365146211, 367979653, 372709, 27285758400832683314699, 102031
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[7^n - 5^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015