English

Product representation of perfect cubes

Combinatorics 2024-05-21 v1 Number Theory

Abstract

Let Fk,d(n)F_{k,d}(n) be the maximal size of a set A[n]{A}\subseteq [n] such that the equation a1a2ak=xd,  a1<a2<<aka_1a_2\dots a_k=x^d, \; a_1<a_2<\ldots<a_k has no solution with a1,a2,,akAa_1,a_2,\ldots,a_k\in {A} and integer xx. Erd\H{o}s, S\'ark\"ozy and T. S\'os studied Fk,2F_{k,2}, and gave bounds when k=2,3,4,6k=2,3,4,6 and also in the general case. We study the problem for d=3d=3, and provide bounds for k=2,3,4,6k=2,3,4,6 and 99, furthermore, in the general case, as well. In particular, we refute an 18 years old conjecture of Verstra\"ete. We also introduce another function fk,df_{k,d} closely related to Fk,dF_{k,d}: While the original problem requires a1,,aka_1, \ldots , a_k to all be distinct, we can relax this and only require that the multiset of the aia_i's cannot be partitioned into dd-tuples where each dd-tuple consists of dd copies of the same number.

Keywords

Cite

@article{arxiv.2405.12088,
  title  = {Product representation of perfect cubes},
  author = {Zsigmond György Fleiner and Márk Hunor Juhász and Blanka Kövér and Péter Pál Pach and Csaba Sándor},
  journal= {arXiv preprint arXiv:2405.12088},
  year   = {2024}
}