Largest prime factor of 4^n - 3^n.
1, 7, 37, 7, 71, 37, 14197, 337, 6553, 181, 174659, 193, 500111, 14197, 601, 4241, 17050729021, 6553, 10814953, 8861, 8352709, 174659, 44483, 51361, 1440528320401, 500111, 36174709, 376853, 295324633, 2131, 687147718331, 4338014017, 496393931749, 17050729021
1
We include the first term even though it is not prime. The n that produce prime 4^n - 3^n are in A059801.
T. D. Noe, Plot of 100 terms
T. D. Noe, Table of 100 terms
Eric W. Weisstein, MathWorld: Greatest Prime Factor
(Mma) Table[FactorInteger[4^n - 3^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015