A077449 Numbers k such that Sum_{d|k} mu(phi(d)) = 0.

3, 6, 15, 30, 31, 39, 43, 51, 57, 62, 67, 71, 75, 78, 79, 86, 87, 102, 103, 111, 114, 123, 131, 134, 139, 142, 147, 150, 155, 158, 159, 174, 183, 191, 195, 206, 215, 219, 222, 223, 239, 246, 255, 262, 267, 278, 279, 283, 285, 291, 294, 303, 310, 311, 318, 327

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Vaclav Kotesovec, Plot of a(n)/n for n = 1..360000

Formula

a(n) seems to be asymptotic to c*n where c is around 5.47...

Mathematica

Select[Range[400], Total[MoebiusMu[EulerPhi[#]]&/@Divisors[#]]==0&] (* Harvey P. Dale, Dec 22 2018 *)
Select[Range[330], DivisorSum[#, MoebiusMu[EulerPhi[#1]] &] == 0 &] (* Amiram Eldar, Sep 08 2020 *)

Prog

(PARI) isok(k) = sumdiv(k, d, moebius(eulerphi(d))) == 0; \\ Michel Marcus, Sep 08 2020

Crossrefs

Cf. A000010, A008683.

Sequence in context: A244705 A319643 A092641 * A356666 A152232 A357007

Adjacent sequences: A077446 A077447 A077448 * A077450 A077451 A077452

Keyword

nonn

Author

Benoit Cloitre, Nov 30 2002

Status

approved