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MathNet 2022-part-06 — 196 problems (EN–VI) Question 125

Math Olympiad Vault · MathNet 2022-part-06 — 196 problems (EN–VI)

Question 125

Compute the number of permutations $\pi$ of the set $\{1,2, \ldots, 10\}$ so that for all (not necessarily distinct) $m, n \in\{1,2, \ldots, 10\}$ where $m+n$ is prime, $\pi(m)+\pi(n)$ is prime.