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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A282570 Number of ways to write n as an ordered sum of two multiplicatively perfect numbers (A007422).

Original entry on oeis.org

0, 0, 1, 0, 0, 0, 0, 2, 0, 2, 0, 2, 1, 0, 2, 2, 5, 0, 2, 0, 3, 2, 4, 4, 2, 2, 0, 4, 5, 4, 3, 2, 4, 2, 4, 6, 8, 4, 0, 4, 6, 8, 5, 6, 5, 4, 2, 8, 10, 8, 2, 0, 7, 6, 7, 4, 8, 4, 2, 8, 10, 12, 2, 6, 4, 10, 9, 6, 9, 4, 7, 6, 14, 12, 2, 6, 5, 10, 7, 10, 8, 4, 4, 10, 14, 8, 6, 6, 10, 8, 10, 12, 15, 8, 6, 14
Offset: 0

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Author

Ilya Gutkovskiy, Feb 18 2017

Keywords

Comments

Conjecture: a(n) > 0 for all n > 51.

Examples

			a(16) = 5 because we have [15, 1], [10, 6], [8, 8], [6, 10] and [1, 15].
		

Crossrefs

Programs

  • Mathematica
    nmax = 95; CoefficientList[Series[Sum[Boole[Sqrt[k]^DivisorSigma[0, k]/k == k] x^k, {k, 1, nmax}]^2, {x, 0, nmax}], x]

Formula

G.f.: (Sum_{k>=1} x^A007422(k))^2.
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