A307428 - OEIS

%I #17 Dec 25 2022 02:11:42

%S 1,-1,-1,1,-1,1,-1,-2,1,1,-1,-1,-1,1,1,2,-1,-1,-1,-1,1,1,-1,2,1,1,-2,

%T -1,-1,-1,-1,-2,1,1,1,1,-1,1,1,2,-1,-1,-1,-1,-1,1,-1,-2,1,-1,1,-1,-1,

%U 2,1,2,1,1,-1,1,-1,1,-1,2,1,-1,-1,-1,1,-1,-1,-2,-1

%N Dirichlet g.f.: zeta(2*s) / (zeta(s) * zeta(3*s)).

%C Dirichlet convolution of A307423 and A008683.

%H Vaclav Kotesovec, <a href="/A307428/b307428.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DirichletGeneratingFunction.html">Dirichlet Generating Function</a>.

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Dirichlet_series">Dirichlet series</a>.

%F Multiplicative with a(p) = -1, a(p^2) = 1, and a(p^e) = 2*(-1)^e for e >= 3. - _Amiram Eldar_, Dec 25 2022

%t nmax = 100; A307423 = Table[DivisorSum[n, Boole[Max[FactorInteger[#][[All, 2]]] < 3] * LiouvilleLambda[n/#]&], {n, 1, nmax}]; Table[DivisorSum[n, MoebiusMu[#] * A307423[[n/#]] &], {n, 1, nmax}]

%t f[p_, e_] := 2*(-1)^e; f[p_, 1] := -1; f[p_, 2] := 1; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* _Amiram Eldar_, Dec 25 2022 *)

%o (PARI) for(n=1, 100, print1(direuler(p=2, n, (1-X^3)/(1+X))[n], ", ")) \\ _Vaclav Kotesovec_, Jun 14 2020

%Y Cf. A008683, A010052, A056624, A307423.

%K sign,mult

%O 1,8

%A _Vaclav Kotesovec_, Apr 08 2019