Numbers n such that 5^n+1 has only one primitive prime factor.
0, 1, 2, 3, 4, 5, 6, 9, 12, 14, 24, 28, 44, 45, 46, 54, 55, 58, 60, 67, 99, 101, 103, 118, 124, 144, 192, 210, 229, 250, 265, 268, 310, 347, 399, 496, 532, 567, 615, 835, 1047, 1081, 1258, 1494, 1944, 2050, 2313, 2397, 2498, 2728, 3324, 3418, 3646, 3862
1
Numbers n such that S000010(n) = 1.
T. D. Noe, Plot of 68 terms
T. D. Noe, Table of 68 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 5; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000010.
nonn,hard
T. D. Noe, Nov 21 2014