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MathNet 2007-part-03 — 185 problems (EN–VI) Question 60

Math Olympiad Vault · MathNet 2007-part-03 — 185 problems (EN–VI)

Question 60

Two sequences of positive integers, $x_{1}, x_{2}, x_{3}, \ldots$ and $y_{1}, y_{2}, y_{3}, \ldots$, are given, such that
$$
y_{n+1} / x_{n+1} \gt y_{n} / x_{n}
$$
for each $n \geq 1$. Prove that there are infinitely many values of $n$ such that $y_{n} \gt \sqrt{n}$.