Decomposing a factorial into large factors

Fuente: arXiv
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Autores principales: Alexeev, Boris, Conway, Evan, Rosenfeld, Matthieu, Sutherland, Andrew V., Tao, Terence, Uhr, Markus, Ventullo, Kevin
Formato: Preprint
Publicado: 2025
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author Alexeev, Boris
Conway, Evan
Rosenfeld, Matthieu
Sutherland, Andrew V.
Tao, Terence
Uhr, Markus
Ventullo, Kevin
author_facet Alexeev, Boris
Conway, Evan
Rosenfeld, Matthieu
Sutherland, Andrew V.
Tao, Terence
Uhr, Markus
Ventullo, Kevin
contents Let $t(N)$ denote the largest number such that $N!$ can be expressed as the product of $N$ integers greater than or equal to $t(N)$. The bound $t(N)/N = 1/e-o(1)$ was apparently established in unpublished work of Erdős, Selfridge, and Straus; but the proof is lost. Here we obtain the more precise asymptotic $$ \frac{t(N)}{N} = \frac{1}{e} - \frac{c_0}{\log N} + O\left( \frac{1}{\log^{1+c} N} \right)$$ for an explicit constant $c_0 = 0.30441901\dots$ and some absolute constant $c>0$, answering a question of Erdős and Graham. For the upper bound, a further lower order term in the asymptotic expansion is also obtained. With numerical assistance, we obtain highly precise computations of $t(N)$ for wide ranges of $N$, establishing several explicit conjectures of Guy and Selfridge on this sequence. For instance, we show that $t(N) \geq N/3$ for $N \geq 43632$, with the threshold shown to be best possible.
format Preprint
id arxiv_https___arxiv_org_abs_2503_20170
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Decomposing a factorial into large factors
Alexeev, Boris
Conway, Evan
Rosenfeld, Matthieu
Sutherland, Andrew V.
Tao, Terence
Uhr, Markus
Ventullo, Kevin
Number Theory
11A51
Let $t(N)$ denote the largest number such that $N!$ can be expressed as the product of $N$ integers greater than or equal to $t(N)$. The bound $t(N)/N = 1/e-o(1)$ was apparently established in unpublished work of Erdős, Selfridge, and Straus; but the proof is lost. Here we obtain the more precise asymptotic $$ \frac{t(N)}{N} = \frac{1}{e} - \frac{c_0}{\log N} + O\left( \frac{1}{\log^{1+c} N} \right)$$ for an explicit constant $c_0 = 0.30441901\dots$ and some absolute constant $c>0$, answering a question of Erdős and Graham. For the upper bound, a further lower order term in the asymptotic expansion is also obtained. With numerical assistance, we obtain highly precise computations of $t(N)$ for wide ranges of $N$, establishing several explicit conjectures of Guy and Selfridge on this sequence. For instance, we show that $t(N) \geq N/3$ for $N \geq 43632$, with the threshold shown to be best possible.
title Decomposing a factorial into large factors
topic Number Theory
11A51
url https://arxiv.org/abs/2503.20170