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2018 IMO Problems/Problem 5

Revision as of 23:39, 10 July 2018 by Btc433 (talk | contribs) (Created page with "Let <math>a_1, a_2, \dots</math> be an infinite sequence of positive integers. Suppose that there is an integer<math> N > 1</math> such that, for each <math>n \geq N</math>, t...")
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Let $a_1, a_2, \dots$ be an infinite sequence of positive integers. Suppose that there is an integer$N > 1$ such that, for each $n \geq N$, the number $\frac{a_1}{a_2}+\frac{a_2}{a_3}+\dots +\frac{a_{n-1}}{a_n}+\frac{a_n}{a_1}$ is an integer. Prove that there is a positive integer $M$ such that $a_m = a_{m+1}$ for all $m \geq M.$

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