An upper bound on the size of Sidon sets

József Balogh, Zoltán Füredi, Souktik Roy

Combining two elementary proofs we decrease the gap between the upper and lower bounds by $0.2\%$ in a classical combinatorial number theory problem. We show that the maximum size of a Sidon set of $\{ 1, 2, \ldots, n\}$ is at most $\sqrt{n}+ 0.998n^{1/4}$ for sufficiently large $n$.

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