An improved lower bound related to the Furstenberg-Sárközy theorem
Let $D(n)$ denote the cardinality of the largest subset of the set $\{1,2,\ldots,n\}$ such that the difference of no pair of distinct elements is a square. A well-known theorem of Furstenberg and Sárközy states that $D(n)=o(n)$. In the other direction, Ruzsa has proven that $D(n) \gtrsim n^{\gamma}$ for $\gamma = \frac{1}{2}\left( 1 + \frac{\log 7}{\log 65} \right) \approx 0.733077$. We improve this to $\gamma = \frac{1}{2}\left( 1 + \frac{\log 12}{\log 205} \right) \approx 0.733412$.
2017 ◽
Vol 26
(12)
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pp. 1750072
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1973 ◽
Vol 29
(02)
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pp. 490-498
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2017 ◽
1953 ◽
Vol 31
(3)
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pp. 447-460
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2020 ◽
Vol 15
(S359)
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pp. 188-189
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