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MathNet 2016-part-07 — 182 problems (EN–VI) Question 175

Math Olympiad Vault · MathNet 2016-part-07 — 182 problems (EN–VI)

Question 175

The vertices of a regular nonagon are colored such that 1) adjacent vertices are different colors and 2) if 3 vertices form an equilateral triangle, they are all different colors.

Let $m$ be the minimum number of colors needed for a valid coloring, and $n$ be the total number of colorings using $m$ colors. Determine $m n$. (Assume each vertex is distinguishable.)