Numbers n such that 7^n+1 has only one primitive prime factor.
0, 2, 3, 4, 9, 14, 15, 17, 18, 23, 24, 25, 27, 29, 38, 42, 47, 61, 74, 112, 140, 144, 148, 166, 176, 228, 264, 325, 327, 365, 370, 513, 730, 830, 1130, 1190, 1445, 1619, 2010, 2358, 2454, 2962, 3170, 3447, 3522, 4098, 4242, 4686, 5024, 6630, 6944, 7099
1
Numbers n such that S000012(n) = 1.
T. D. Noe, Plot of 57 terms
T. D. Noe, Table of 57 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 7; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[2, 1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000012.
nonn,hard
T. D. Noe, Nov 21 2014