Numbers n such that 4^n+1 has only one primitive prime factor.
0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 20, 30, 46, 48, 52, 70, 74, 78, 150, 178, 204, 298, 306, 346, 366, 378, 400, 476, 498, 502, 614, 634, 1120, 1266, 1530, 1898, 1912, 1972, 2548, 2770, 3738, 3850, 4272, 4900, 7314, 7914, 8454, 9240
1
Numbers n such that S000009(n) = 1.
T. D. Noe, Plot of 48 terms
T. D. Noe, Table of 48 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 4; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000009.
nonn,hard
T. D. Noe, Nov 21 2014