Numbers n such that 3^n+1 has only one primitive prime factor.
0, 2, 3, 4, 5, 6, 7, 10, 12, 13, 16, 18, 20, 23, 30, 32, 35, 36, 43, 54, 64, 65, 66, 77, 118, 138, 152, 182, 215, 232, 264, 281, 336, 340, 359, 380, 391, 414, 446, 487, 492, 529, 535, 540, 577, 624, 713, 720, 731, 762, 799, 1066, 1094, 1098, 1170, 1230, 1254
1
Numbers n such that S000008(n) = 1.
T. D. Noe, Plot of 99 terms
T. D. Noe, Table of 99 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 3; f2[n_] := Cyclotomic[2*n, d]/Cyclotomic[n, d]; Join[{0}, Select[Range[2, 1000], PrimePowerQ[f2[#]/GCD[f2[#], #]] &]]
Cf. S000008.
nonn,hard
T. D. Noe, Nov 21 2014