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USAJMO 2012 Question 2

USAJMO · USAJMO 2012

Question 2

Find all integers $n \ge 3$ such that among any $n$ positive real numbers
$a_1$, $a_2$, …, $a_n$ with

\[\max(a_1,a_2,\dots,a_n)
\le n \cdot \min(a_1,a_2,\dots,a_n),\]

there exist three that are the side lengths of an acute triangle.

Proposed by Titu Andreescu (credit in the supplied notes).