OFFSET
1
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 1..10000
Vaclav Kotesovec, Graph - the asymptotic ratio.
Eric Weisstein's World of Mathematics, Dirichlet Generating Function.
Wikipedia, Dirichlet series.
FORMULA
Sum_{k=1..n} a(k) ~ 6*n / (Pi^2 * zeta(3)).
Multiplicative with a(p) = 1, a(p^e) = -1 if e = 3 or 4, and 0 if e = 2 or e >= 5. - Amiram Eldar, Dec 25 2022
MATHEMATICA
nmax = 100; A271102 = Table[DivisorSum[n, Abs[MoebiusMu[#]]*MoebiusMu[n/#] &], {n, 1, nmax}]; Table[DivisorSum[n, Boole[Max[FactorInteger[#][[All, 2]]] < 3] * A271102[[n/#]] &], {n, 1, nmax}]
f[p_, e_] := Switch[e, 1, 1, 3, -1, 4, -1, _, 0]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Dec 25 2022 *)
PROG
(PARI) for(n=1, 100, print1(direuler(p=2, n, (1+X)*(1-X^3))[n], ", ")) \\ Vaclav Kotesovec, Jun 14 2020
CROSSREFS
KEYWORD
sign,mult
AUTHOR
Vaclav Kotesovec, Apr 08 2019
STATUS
approved