On the two-colour Rado number for $\sum_{i=1}^m a_ix_i=c$

TL;DR

This paper investigates the two-colour Rado number for linear equations of the form a_ix_i=c, introducing the concept of t-distributability to determine exact values and bounds, thereby generalizing previous results in the field.

Contribution

The paper introduces t-distributability and provides exact values and bounds for the two-colour Rado number in specific cases, extending prior research.

Findings

Exact Rado numbers for 2- and 3-distributable sets when a_m=-1 and r=2.

Upper and lower bounds for cases where exact values are not determined.

Generalization of previous results in Rado number theory.

Abstract

Let $a_1,\ldots,a_m$ be nonzero integers, $c \in \mathbb Z$ and $r \ge 2$. The Rado number for the equation \[ \sum_{i=1}^m a_ix_i = c \] in $r$ colours is the least positive integer $N$ such that any $r$-colouring of the integers in the interval $[1,N]$ admits a monochromatic solution to the given equation. We introduce the concept of $t$-distributability of sets of positive integers, and determine exact values whenever possible, and upper and lower bounds otherwise, for the Rado numbers when the set $\{a_1,\ldots,a_{m-1}\}$ is $2$-distributable or $3$-distributable, $a_m=-1$, and $r=2$. This generalizes previous works by several authors.