OFFSET
1,1
COMMENTS
Also numbers k such that mu(k) = -Sum_{d|k, d not a perfect power} mu(k/d).
Contains all squarefree numbers (A005117) except 1.
The numbers of terms not exceeding 10^k, for k = 1, 2, ..., are 7, 74, 746, 7443, 74337, 743235, 7432161, 74320977, 743208896, 7432087549, ... . Apparently, the asymptotic density of this sequence exists and equals 0.743208... . - Amiram Eldar, May 20 2023
LINKS
Andrew Howroyd, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[100], Sum[If[GCD@@FactorInteger[d][[All, 2]]===1, MoebiusMu[#/d], 0], {d, Divisors[#]}]===0&]
PROG
(PARI) ok(n)={sumdiv(n, d, if(ispower(d), 0, moebius(n/d))) == 0} \\ Andrew Howroyd, Aug 26 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 11 2018
STATUS
approved