Largest prime factor of 9^n - 8^n.
1, 17, 31, 29, 641, 73, 2685817, 10657, 1166833, 641, 990918479, 421, 303999697, 2685817, 9151, 103681, 140052251320207, 1166833, 15678079, 1021, 24559217887, 990918479, 1878420820626737, 22129, 171382356359199751, 181860096601, 100693360657, 2685817
1
We include the first term even though it is not prime. The n that produce prime 9^n - 8^n are in A059803.
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 - 8^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015