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# Help

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Let $a_1,$ $a_2,$ $\dots$ be a sequence of real numbers such that for all positive integers $n,$ $\sum_{k = 1}^n a_k \left( \frac{k}{n} \right)^2 = 1.$Find the smallest $n$ such that $a_n < \frac{1}{2018}.$

Aug 25, 2021