cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A326815 Dirichlet g.f.: zeta(s)^3 * Product_{p prime} (1 - 2 * p^(-s)).

Original entry on oeis.org

1, 1, 1, 0, 1, 1, 1, -2, 0, 1, 1, 0, 1, 1, 1, -5, 1, 0, 1, 0, 1, 1, 1, -2, 0, 1, -2, 0, 1, 1, 1, -9, 1, 1, 1, 0, 1, 1, 1, -2, 1, 1, 1, 0, 0, 1, 1, -5, 0, 0, 1, 0, 1, -2, 1, -2, 1, 1, 1, 0, 1, 1, 0, -14, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, -5, -5, 1, 1, 0, 1
Offset: 1

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Author

Ilya Gutkovskiy, Oct 19 2019

Keywords

Comments

Inverse Moebius transform applied twice to A076479 (unitary Moebius function).

Crossrefs

Cf. A000005, A001221, A005117 (positions of 1's), A007425, A008683, A038109 (positions of 0's), A046951, A076479, A080956, A326814.

Programs

  • Mathematica
    Table[Sum[(-1)^PrimeNu[n/d] DivisorSigma[0, d], {d, Divisors[n]}], {n, 1, 85}]
    f[p_, e_] := (e + 1)*(2 - e)/2; a[1] = 1; a[n_] := Times @@ (f @@@ FactorInteger[n]); Array[a, 100] (* Amiram Eldar, Oct 26 2020 *)
  • PARI
    A326815(n) = sumdiv(n,d,((-1)^omega(n/d))*numdiv(d)); \\ Antti Karttunen, Nov 17 2019
    
  • PARI
    for(n=1, 100, print1(direuler(p=2, n, (1 - 2*X)/(1 - X)^3)[n], ", ")) \\ Vaclav Kotesovec, Aug 22 2021

Formula

a(n) = Sum_{d|n} (-1)^omega(n/d) * tau(d), where omega = A001221 and tau = A000005.
a(n) = Sum_{d|n} tau_3(n/d) * mu(d) * 2^omega(d), where tau_3 = A007425 and mu = A008683.
Multiplicative with a(p^e) = (e+1)*(2-e)/2 = A080956(e). - Amiram Eldar, Oct 26 2020
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