On common divisors of multinomial coefficients

TL;DR

This paper establishes a lower bound for common divisors of certain multinomial coefficients, advances understanding of their divisibility properties, and refines conditions related to Wasserman's conjecture.

Contribution

It provides a proven lower bound on common divisors of multinomial coefficients and narrows the class of potential counterexamples to Wasserman's conjecture.

Findings

A lower bound on the common divisor that grows with the sum of parameters.

Identification of conditions narrowing possible counterexamples to Wasserman's conjecture.

Demonstration that some plausible generalizations of Wasserman's conjecture are false.

Abstract

Erd\H{o}s and Szekeres showed in 1978 that for any four positive integers satisfying m_1+m_2 = n_1+n_2, the two binomial coefficients (m_1+m_2)!/m_1! m_2! and (n_1+n_2)!/n_1! n_2! have a common divisor >1. The analogous statement for families of k k-nomial coefficients (k>1) was conjectured in 1997 by David Wasserman. Erd\H{o}s and Szekeres remark that if m_1, m_2, n_1, n_2 as above are all >1, there is probably a lower bound on the common divisor in question which goes to infinity as a function of m_1+m_2. Such a bound is here obtained. Results are proved that narrow the class of possible counterexamples to Wasserman's conjecture. On the other hand, several plausible generalizations of that conjecture are shown to be false.