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MathNet 2024-part-01 — 168 problems (EN–VI) Question 73

Math Olympiad Vault · MathNet 2024-part-01 — 168 problems (EN–VI)

Question 73

Let $N$ be a positive integer. The sequence $x_1, x_2, \dots$ of non-negative reals is defined by
$$
x_n^2 = \sum_{i=1}^{n-1} \sqrt{x_i x_{n-i}}
$$
for all positive integers $n \gt N$. Show that there exists a constant $c \gt 0$, such that $x_n \le \frac{n}{2} + c$ for all positive integers $n$.