Numbers n such that 8^n+1 has only one primitive prime factor.
0, 1, 3, 9, 15, 21, 39, 57, 69, 159, 165, 204, 231, 252, 501, 873, 897, 1020, 1209, 1395, 1947, 2361, 3369, 7305, 7308, 7647, 8331, 9483
1
Numbers n such that S000013(n) = 1.
T. D. Noe, Plot of 28 terms
T. D. Noe, Table of 28 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 8; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000013.
nonn,hard,more
T. D. Noe, Nov 21 2014