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arXiv · 1207.0432

The 2-color Rado number of $x_1+x_2+...+x_{m-1}=ax_m$

Dan Saracino
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Abstract

In 1982, Beutelspacher and Brestovansky proved that for every integer $m\geq 3,$ the 2-color Rado number of the equation $$x_1+x_2+...+x_{m-1}=x_m$$ is $m^2-m-1.$ In 2008, Schaal and Vestal proved that, for every $m\geq 6,$ the 2-color Rado number of $$x_1+x_2+...+x_{m-1}=2x_m$$ is $\lceil \frac{m-1}{2}\lceil\frac{m-1}{2}\rceil\rceil.$ Here we prove that, for every integer $a\geq 3$ and every $m\geq 2a^2-a+2$, the 2-color Rado number of $$x_1+x_2+...+x_{m-1}=ax_m$$ is $\lceil\frac{m-1}{a}\lceil\frac{m-1}{a}\rceil\rceil.$ For the case $a=3,$ we show that our formula gives the Rado number for all $m\geq 7,$ and we determine the Rado number for all $m\geq 3.$

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Dan Saracino. 2013-01-08. The 2-color Rado number of $x_1+x_2+...+x_{m-1}=ax_m$. https://arxiv.org/abs/1207.0432

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