On the two-colour Rado number for ${\sum }_{i=1}^m{a}_i{x}_i=c$

Abstract

Let $a_1,\dots ,a_m$ 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 $\{a_1,\dots ,a_{m-1}\}$ is $2$-distributable or $3$-distributable, $a_m=-1$, and $r=2$. This generalizes previous works by several authors.

One table of summary, 25 referenecs, 17 pages