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MathNet 2023-part-06 — 191 problems (EN–VI) Question 128

Math Olympiad Vault · MathNet 2023-part-06 — 191 problems (EN–VI)

Question 128

Find all positive integers $n \ge 3$ such that
$$
n! \mid \prod_{\substack{p \lt q \le n, \\ p,q \text{ primes}}} (p+q).
$$
That is, $n!$ divides the product $\prod_{p \lt q \le n,\ p,q\ \text{primes}} (p+q)$.