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.

Showing 1-2 of 2 results.

A334744 a(1) = 1; a(n) = -Sum_{d|n, d < n} bigomega(n/d) * a(d), where bigomega = A001222.

Original entry on oeis.org

1, -1, -1, -1, -1, 0, -1, 0, -1, 0, -1, 2, -1, 0, 0, 1, -1, 2, -1, 2, 0, 0, -1, 2, -1, 0, 0, 2, -1, 3, -1, 1, 0, 0, 0, 2, -1, 0, 0, 2, -1, 3, -1, 2, 2, 0, -1, -1, -1, 2, 0, 2, -1, 2, 0, 2, 0, 0, -1, 0, -1, 0, 2, 0, 0, 3, -1, 2, 0, 3, -1, -3, -1, 0, 2, 2, 0, 3, -1, -1, 1, 0, -1, 0, 0, 0, 0, 2, -1, 0, 0, 2
Offset: 1

Views

Author

Ilya Gutkovskiy, May 09 2020

Keywords

Comments

Dirichlet inverse of A086436. - Antti Karttunen, Nov 29 2024

Crossrefs

Cf. A001222, A007427, A069513, A086436 (Dirichlet inverse), A327276, A334743.

Programs

  • Mathematica
    a[n_] := If[n == 1, n, -Sum[If[d < n, PrimeOmega[n/d] a[d], 0], {d, Divisors[n]}]]; Table[a[n], {n, 92}]
  • PARI
    memoA334744 = Map();
    A334744(n) = if(1==n,1,my(v); if(mapisdefined(memoA334744,n,&v), v, v = -sumdiv(n,d,if(dA334744(d),0)); mapput(memoA334744,n,v); (v))); \\ Antti Karttunen, Nov 29 2024

Formula

G.f. A(x) satisfies: A(x) = x - Sum_{k>=2} bigomega(k) * A(x^k).
Dirichlet g.f.: 1 / (1 + zeta(s) * Sum_{k>=1} primezeta(k*s)).

A341444 Dirichlet inverse of A083399, where A083399(n) = 1 + omega(n).

Original entry on oeis.org

1, -2, -2, 2, -2, 5, -2, -2, 2, 5, -2, -7, -2, 5, 5, 2, -2, -7, -2, -7, 5, 5, -2, 9, 2, 5, -2, -7, -2, -16, -2, -2, 5, 5, 5, 14, -2, 5, 5, 9, -2, -16, -2, -7, -7, 5, -2, -11, 2, -7, 5, -7, -2, 9, 5, 9, 5, 5, -2, 30, -2, 5, -7, 2, 5, -16, -2, -7, 5, -16, -2, -23, -2, 5, -7, -7, 5, -16, -2, -11, 2, 5, -2, 30, 5, 5, 5, 9, -2, 30, 5
Offset: 1

Views

Author

Michel Marcus, Feb 12 2021

Keywords

Comments

The Dirichlet inverse function, a(n) = (omega + 1)^(-1)(n). - Original name.

Crossrefs

Dirichlet inverse of A083399.
Cf. A001221, A001222, A008480, A008683, A008966, A341472 (partial sums).
Cf. also A334743.

Programs

  • Mathematica
    a[1] = 1; a[n_] := a[n] = -DivisorSum[n, (PrimeNu[n/#] + 1)*a[#] &, # < n &]; Array[a, 100] (* Amiram Eldar, Jul 21 2022 *)
  • PARI
    cOmega(n) = if (n==1, 1, my(f=factor(n)); bigomega(n)!*prod(k=1, #f~, 1/f[k,2]!)); \\ A008480
    a(n) = (-1)^bigomega(n)*sumdiv(n, d, moebius(n/d)^2*cOmega(d));
    
  • PARI
    memoA341444 = Map();
    A341444(n) = if(1==n,1,my(v); if(mapisdefined(memoA341444,n,&v), v, v = -sumdiv(n,d,if(dA341444(d),0)); mapput(memoA341444,n,v); (v))); \\ Antti Karttunen, Jul 21 2022~

Formula

a(n) = (-1)^A001222(n)*Sum_{d | n} A008683(n/d)^2*A008480(d).
a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, dA083399(n/d) * a(d). - Antti Karttunen, Jul 21 2022

Extensions

Data section extended up to a(91) and name edited by Antti Karttunen, Jul 21 2022
Showing 1-2 of 2 results.