English

On practical sets and $A$-practical numbers

Number Theory 2024-05-29 v1

Abstract

Let AA be a set of positive integers. We define a positive integer nn as an AA-practical number if every positive integer from the set {1,,dA,dnd}\left\{1,\ldots ,\sum_{d\in A, d\mid n}d\right\} can be written as a sum of distinct divisors of nn that belong to AA. Denote the set of AA-practical numbers as Pr(A)\text{Pr}(A). The aim of the paper is to explore the properties of the sets Pr(A)\text{Pr}(A) (the form of the elements, cardinality) as AA varies over the power set of N\mathbb{N}. We are also interested in the set-theoretic and dynamic properties of the mapping PR:P(N)APr(A)P(N)\mathcal{PR}:\mathcal{P}(\mathbb{N})\ni A\mapsto\text{Pr}(A)\in\mathcal{P}(\mathbb{N}).

Keywords

Cite

@article{arxiv.2405.18225,
  title  = {On practical sets and $A$-practical numbers},
  author = {Andrzej Kukla and Piotr Miska},
  journal= {arXiv preprint arXiv:2405.18225},
  year   = {2024}
}

Comments

This is a preliminary version of the paper

R2 v1 2026-06-28T16:43:55.830Z