OFFSET
1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..100000
FORMULA
Multiplicative with a(p^e) = 0 if p <= 3 or e >= 2, and 1 otherwise.
From Amiram Eldar, May 29 2024: (Start)
Dirichlet g.f.: (2^s/(2^s+1)) * (3^s/(3^s+1)) * zeta(s)/zeta(2*s).
Sum_{k=1..n} a(k) ~ (3/Pi^2) * n. (End)
MATHEMATICA
a[n_] := If[SquareFreeQ[6*n], 1, 0]; Array[a, 100] (* Amiram Eldar, May 29 2024 *)
PROG
CROSSREFS
KEYWORD
nonn,easy,mult
AUTHOR
Antti Karttunen, May 28 2024
STATUS
approved