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MathNet 2007-part-02 — 187 problems (EN–VI) Question 132

Math Olympiad Vault · MathNet 2007-part-02 — 187 problems (EN–VI)

Question 132

Let $n \geq 1$. Find all permutations $(a_1, a_2, \ldots, a_n)$ of $(1,2, \ldots, n)$ for which
$$
\frac{a_k^2}{a_{k+1}} \leq k+2 \quad \text{for } k=1,2, \ldots, n-1
$$