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.

A353421 Dirichlet convolution of A353269 with A353348 (the Dirichlet inverse of A353350).

Original entry on oeis.org

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

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Author

Antti Karttunen, Apr 19 2022

Keywords

Comments

Dirichlet convolution between this sequence and A353352 is A353362.

Crossrefs

Cf. A353422 (Dirichlet inverse).

Programs

  • PARI
    up_to = 65537;
    DirInverseCorrect(v) = { my(u=vector(#v)); u[1] = (1/v[1]); for(n=2, #v, u[n] = (-u[1]*sumdiv(n, d, if(dA048675(n) = { my(f = factor(n)); sum(k=1, #f~, f[k, 2]*2^primepi(f[k, 1]))/2; };
    A353350(n) = (0==(A048675(n)%3));
    v353348 = DirInverseCorrect(vector(up_to,n,A353350(n)));
    A353348(n) = v353348[n];
    A156552(n) = { my(f = factor(n), p, p2 = 1, res = 0); for(i = 1, #f~, p = 1 << (primepi(f[i, 1]) - 1); res += (p * p2 * (2^(f[i, 2]) - 1)); p2 <<= f[i, 2]); res };
    A353269(n) = (!(A156552(n)%3));
    A353421(n) = sumdiv(n,d,A353269(n/d)*A353348(d));

Formula

a(n) = Sum_{d|n} A353269(n/d) * A353348(d).
a(n) = a(A003961(n)) = a(A348717(n)), for all n >= 1.