Numbers n such that 9^n+1 has only one primitive prime factor.
0, 1, 2, 3, 5, 6, 8, 9, 10, 15, 16, 18, 27, 32, 33, 59, 69, 76, 91, 116, 132, 168, 170, 190, 207, 223, 246, 270, 312, 360, 381, 533, 547, 549, 585, 615, 627, 660, 714, 773, 1009, 1287, 1362, 1402, 1460, 1537, 1658, 1823, 2062, 2066, 2093, 2310, 2401, 2733
1
Numbers n such that S000014(n) = 1.
T. D. Noe, Plot of 63 terms
T. D. Noe, Table of 63 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 9; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000014.
nonn,hard
T. D. Noe, Nov 21 2014