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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A365637 a(n) is the smallest number k such that k*n is a term of A072873.

Original entry on oeis.org

1, 2, 9, 1, 625, 18, 117649, 2, 3, 1250, 25937424601, 9, 23298085122481, 235298, 5625, 1, 48661191875666868481, 6, 104127350297911241532841, 625, 1058841, 51874849202, 907846434775996175406740561329, 18, 125, 46596170244962, 1, 117649, 88540901833145211536614766025207452637361
Offset: 1

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Author

Amiram Eldar, Sep 14 2023

Keywords

Crossrefs

Programs

  • Mathematica
    f[p_, e_] := p^(Ceiling[e/p]*p - e); a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 30]
  • PARI
    a(n) = {my(f = factor(n)); prod(i = 1, #f~, f[i,1]^(f[i,1] * ceil(f[i,2] / f[i,1]) - f[i,2]));}

Formula

Multiplicative with a(p^e) = p^(p*ceiling(e/p) - e).
a(n) = A365636(n)/n.
a(n) >= 1 with equality if and only if n is in A072873.

Extensions

Data, formulas and codes corrected by Amiram Eldar, Feb 15 2024
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