Numbers n such that 4^n-1 has only one primitive prime factor.
1, 2, 3, 4, 6, 8, 10, 12, 16, 20, 28, 40, 60, 92, 96, 104, 140, 148, 156, 300, 356, 408, 596, 612, 692, 732, 756, 800, 952, 996, 1004, 1228, 1268, 2240, 2532, 3060, 3796, 3824, 3944, 5096, 5540, 7476, 7700, 8544, 9800
1
Numbers n such that S000002(n) = 1.
T. D. Noe, Plot of 45 terms
T. D. Noe, Table of 45 terms
Eric W. Weisstein, MathWorld: Primitive Prime Factor
(Mma) d = 4; Select[Range[1000], PrimePowerQ[Cyclotomic[#, d]/GCD[Cyclotomic[#, d], #]] &]
Cf. A161508 (2^n-1 case), S000002, S000360-S000366.
nonn,hard,more
T. D. Noe, Nov 20 2014