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.

A295829 Unitary pseudoperfect numbers that equal to the sum of a subset of their aliquot unitary divisors in a single way.

Original entry on oeis.org

6, 60, 78, 90, 102, 114, 138, 150, 174, 186, 222, 246, 258, 282, 294, 318, 354, 366, 402, 426, 438, 474, 498, 534, 582, 606, 618, 642, 654, 678, 726, 750, 762, 786, 822, 834, 894, 906, 942, 978, 1002, 1014, 1038, 1074, 1086, 1146, 1158, 1182, 1194, 1266, 1338
Offset: 1

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Author

Amiram Eldar, Nov 28 2017

Keywords

Comments

The unitary version of A064771.
It appears that most of the terms are divisible by 3. Terms that are not divisible by 3 are 3770, 5530, 7210, 7630, ... - Michel Marcus, Dec 15 2017
The least odd term is 442365. - Amiram Eldar, Jun 10 2020

Examples

			150 is in the sequence since its aliquot unitary divisors are 1, 2, 3, 6, 25, 50, 75 and there is only one subset whose sum is 150: {25, 50, 75}.
		

Crossrefs

Programs

  • Mathematica
    ud[n_] := Block[{d = Divisors[n]}, Select[d, GCD[#, n/#] == 1 &]];
    a = {}; n = 0; While[Length[a] < 100, n++; d = Most[ud[n]];
    c = SeriesCoefficient[Series[Product[1 + x^d[[i]], {i, Length[d]}], {x, 0, n}], n]; If[c ==1, AppendTo[a, n]]]; a