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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A054018 Squares mentioned in A054017.

Original entry on oeis.org

9, 1, 16, 9, 25, 16, 25, 49, 16, 1, 64, 121, 36, 81, 64, 169, 64, 36, 100, 225, 64, 36, 121, 36, 169, 49, 361, 225, 1, 144, 441, 441, 144, 256, 400, 196, 64, 441, 1, 144, 361, 64, 400, 441, 729, 64, 196, 144, 729, 100, 841, 729, 25, 400, 256, 1225, 100, 729, 1225
Offset: 1

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Author

Asher Auel, Jan 19 2000

Keywords

Comments

If Chowla's function of n read (modulo n) is a nonzero square, print this square.
Chowla's function (A048050) = sum of divisors of n except 1 and n.

Links

Crossrefs

Cf. A048050, A054013, A054017, A054019.

Programs

  • Mathematica
    chowla[n_] := DivisorSigma[1, n] - n - 1; aQ[n_] := (c = chowla[n]) > 0 && IntegerQ @ Sqrt @ Mod[c, n]; Mod[chowla[#], #] & /@ Select[Range[1000], aQ] (* Amiram Eldar, Aug 28 2019 *)
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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