Irregular table of primitive prime factors of 6^n + 1.
7, 37, 31, 1297, 11, 101, 13, 97, 29, 197, 17, 98801, 46441, 241, 6781, 51828151, 1678321, 53, 937, 37571, 421, 5030761, 1950271, 353, 1697, 4709377, 190537, 12690943, 73, 541, 55117, 1787, 48713705333, 41, 68754507401, 2527867231, 58477, 70489, 863017
1
T. D. Noe, Plot of irregular table up to n = 100
T. D. Noe, Table up to n = 100
Wikipedia, Cunningham project
(Mma) pp = {}; t = Table[f = Transpose[FactorInteger[6^n + 1]][[1]]; p = Complement[f, pp]; pp = Union[pp, p]; p, {n, 30}]; Flatten[t]
Cf. S000011 (number of primitive prime factors of 6^n + 1).
nonn,tabf
T. D. Noe, May 14 2014