Ramsey equivalence of $K_n$ and $K_n+K_{n-1}$

Abstract

We prove that, for $n\ge 4$, the graphs $K_n$ and $K_n+K_{n-1}$ are Ramsey equivalent. That is, if $G$ is such that any red-blue colouring of its edges creates a monochromatic $K_n$ then it must also possess a monochromatic $K_n+K_{n-1}$.