ERDŐS TRACKER

CURRENT TOTALS *COMMUNITY DATABASE / 579 SOLVED / 642 REMAINING / 47.42%
SOLVE HISTORY / INTERACTIVE1221 CATALOGUEDDATA AS OF 22 OCT 2026, 12:43:52 UTC
CALENDAR TIME: LINEAR
% OF CURRENT CATALOGUEUse the controls to change the metric, time scale, and graph style. Move across the graph or use the arrow keys to inspect values.0%10%20%30%40%50%194019601980200020202026% OF CURRENT CATALOGUE47.42%579 / 1221 SOLVEDSCALE 0—50%
PROBLEM #863Let r\geq 2 and let A\subseteq \{1,\ldots,N\} be a set of maximal size such that there are at most r solutions to n=a+b with a\leq b for any n. (That is, A is a B_2[r] set.)Similarly, let B\subseteq \{1,\ldots,N\} be a set of maximal size such that there are at most r solutions to n=a-b for any n\geq 1. If \lvert A\rvert\sim c_rN^{1/2} as N\to \infty and \lvert B\rvert \sim c_r'N^{1/2} as N\to \infty then is it true that c_r\neq c_r' for r\geq 2? Is it true that c_r'<c_r?1930OPEN ↗

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Totals from the Erdős community database, checked every ten minutes. The official website stopped publishing solved counts on 6 October 2026. Created by willdepue and GPT-5.6 Sol.

The chart uses reviewed historical resolution dates and may not cover every problem in the current totals. Website status changes can lag the mathematics.