Numbers n such that 6^n+1 has only one primitive prime factor.
0, 1, 2, 3, 4, 9, 11, 12, 15, 21, 25, 31, 43, 45, 47, 59, 62, 72, 77, 93, 96, 107, 177, 180, 240, 279, 382, 407, 437, 514, 525, 551, 579, 688, 732, 734, 811, 891, 917, 962, 1048, 1088, 1232, 1408, 1719, 2088, 2176, 2248, 2724, 2819, 3180, 3515, 3575, 4269
1
Numbers n such that S000011(n) = 1.
T. D. Noe, Plot of 66 terms
T. D. Noe, Table of 66 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 6; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000011.
nonn,hard
T. D. Noe, Nov 21 2014