Largest prime factor of 7^n - 6^n.
1, 13, 127, 17, 821, 127, 543607, 3697, 12547, 821, 18140783, 1933, 20021093, 543607, 3729391, 21089, 726751, 90217, 25565862643, 19681, 1554841, 18140783, 565511002489942841, 4332721, 146934809201, 650589967, 93637, 26412541
1
We include the first term even though it is not prime. The n that produce prime 7^n - 6^n are in A062573.
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 - 6^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015