Largest prime factor of 7^n - 4^n.
3, 11, 31, 13, 5261, 37, 2381, 2657, 2521, 5261, 657710813, 1873, 608942777, 2633, 7681, 2657, 752793961547, 99793, 10977061, 872381, 665953, 657710813, 1500797, 2657, 78871651, 608942777, 374471275609, 23247953, 228982248320251, 7681, 646156690987649, 58954561
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 - 4^n][[-1, 1]], {n, 40}]
nonn
T. D. Noe, Jun 08 2015