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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A346241 Dirichlet inverse of pointwise sum of A003415 (arithmetic derivative of n) and A063524 (1, 0, 0, 0, ...).

Original entry on oeis.org

1, -1, -1, -3, -1, -3, -1, -5, -5, -5, -1, -1, -1, -7, -6, -3, -1, -2, -1, -5, -8, -11, -1, 17, -9, -13, -16, -9, -1, 3, -1, 11, -12, -17, -10, 33, -1, -19, -14, 19, -1, 1, -1, -17, -14, -23, -1, 63, -13, -14, -18, -21, -1, 28, -14, 21, -20, -29, -1, 76, -1, -31, -22, 45, -16, -3, -1, -29, -24, -9, -1, 112, -1, -37, -22, -33
Offset: 1

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Author

Antti Karttunen, Jul 13 2021

Keywords

Crossrefs

Cf. A003415, A354806, A354807, A354808 (positions of negative terms), A354809 (of terms >= 0), A354818 (of even terms).

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(dA003415plusA063524(n) = if(n<=1, 1, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
    v346241 = DirInverseCorrect(vector(up_to,n,A003415plusA063524(n)));
    A346241(n) = v346241[n];
    
  • PARI
    A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
    memoA346241 = Map();
    A346241(n) = if(1==n,1,my(v); if(mapisdefined(memoA346241,n,&v), v, v = -sumdiv(n,d,if(dA003415(n/d)*A346241(d),0)); mapput(memoA346241,n,v); (v)));

Formula

a(1) = 1, and for n > 1, a(n) = -Sum_{d|n, dA003415(n/d) * a(d).
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