Numbers n such that 6^n-1 has only one primitive prime factor.
1, 2, 3, 4, 5, 6, 7, 8, 18, 21, 22, 24, 29, 30, 42, 50, 62, 71, 86, 90, 94, 118, 124, 127, 129, 144, 154, 186, 192, 214, 271, 354, 360, 411, 480, 509, 558, 575, 663, 764, 814, 825, 874, 1028, 1049, 1050, 1102, 1113, 1131, 1158, 1376, 1464, 1468, 1535, 1622
1
Numbers n such that S000004(n) = 1.
T. D. Noe, Plot of 84 terms
T. D. Noe, Table of 84 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 6; Select[Range[1000], PrimePowerQ[Cyclotomic[#, d]/GCD[Cyclotomic[#, d], #]] &]
Cf. A161508 (2^n-1 case), S000004, S000360-S000366.
nonn,hard
T. D. Noe, Nov 20 2014