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
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Nov 30 2002
STATUS
approved