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MathNet 2002 — Part 02 Question 142

Math Olympiad Vault · MathNet 2002 — Part 02

Question 142

Prove that there exist an integer $m \ge 2002$ and $m$ distinct positive integers $a_1, a_2, \dots, a_m$ such that the number
$$
\prod_{i=1}^{m} a_i^2 - 4 \sum_{i=1}^{m} a_i^2
$$
is a perfect square.