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.

A335199 Infinitary Zumkeller numbers (A335197) whose set of infinitary divisors can be partitioned into two disjoint sets of equal sum in a single way.

Original entry on oeis.org

6, 56, 60, 70, 72, 88, 90, 104, 3040, 3230, 3770, 4030, 4510, 5170, 5390, 5800, 5830, 6808, 7144, 7192, 7400, 7912, 8056, 8968, 9272, 9656, 9928, 10744, 10792, 11016, 11096, 11288, 11392, 12104, 12416, 12928, 13184, 13192, 13696, 13736, 13952, 14008, 14464, 14552
Offset: 1

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Author

Amiram Eldar, May 26 2020

Keywords

Examples

			6 is a term since there is only one partition of its set of nonunitary divisors, {1, 2, 3, 6}, into two disjoint sets of equal sum: {1, 2, 3} and {6}.
		

Crossrefs

The infinitary version of A083209.
Subsequence of A335197.

Programs

  • Mathematica
    infdivs[n_] := If[n == 1, {1}, Sort @ Flatten @ Outer[Times, Sequence @@ (FactorInteger[n] /. {p_, m_Integer} :> p^Select[Range[0, m], BitOr[m, #] == m &])]]; infZumQ[n_] := Module[{d = infdivs[n], sum, x}, sum = Plus @@ d; If[sum < 2*n || OddQ[sum], False, CoefficientList[Product[1 + x^i, {i, d}], x][[1 + sum/2]] == 2]]; Select[Range[15000], infZumQ] (* after Michael De Vlieger at A077609 *)