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MathNet 2023-part-05 — 191 problems (EN–VI) Question 55

Math Olympiad Vault · MathNet 2023-part-05 — 191 problems (EN–VI)

Question 55

In an art museum, $n$ paintings are exhibited, where $n \ge 33$ is a positive integer, and a total of 15 colors are used in such a way that any two paintings have at least one color in common, and no two paintings have exactly the same set of colors. Determine all possible values of $n \ge 33$ such that, no matter how we color the paintings with the above properties, we can choose four distinct paintings that we number $T_1, T_2, T_3$, and $T_4$ in such a way that any color used both in $T_1$ and $T_2$ is also used in $T_3$ or $T_4$.