OFFSET
1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..100000
FORMULA
Multiplicative with a(2^e) = 1 if e is even, 0 if e is odd, a(3^e) = 0, and a(p^e) = 1 for any prime p > 3.
From Amiram Eldar, May 29 2024: (Start)
Dirichlet g.f.: (2^s/(2^s+1)) * (1-1/3^s) * zeta(s).
Sum_{k=1..n} a(k) ~ (4/9) * n. (End)
MATHEMATICA
a[n_] := If[EvenQ[IntegerExponent[n, 2]] && !Divisible[n, 3], 1, 0]; Array[a, 100] (* Amiram Eldar, May 29 2024 *)
PROG
CROSSREFS
KEYWORD
nonn,mult,easy
AUTHOR
Antti Karttunen, May 28 2024
STATUS
approved