Article
Keywords:
complete vertex colouring; achromatic number; Cartesian product; complete graph
Summary:
The achromatic number of a graph  $G$ is the maximum number of colours in a proper vertex colouring of  $G$ such that for any two distinct colours there is an edge of  $G$ incident with vertices of those two colours. We determine the achromatic number of the Cartesian product of  $K_5$ and $K_n$ for all $n \le 24$.
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