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The Erdős–Szekeres conjecture on convex polygons

Is 2^(n−2) + 1 points always enough to force a convex n-gon? Known exactly only up to n = 6.

Inferred from the community field; finer classification has not been reviewed.

Problem statement

Let ES(n)\mathrm{ES}(n) be the least NN such that any NN points in general position in the plane contain nn in convex position. Conjecture: ES(n)=2n−2+1\mathrm{ES}(n) = 2^{n-2} + 1.

Lean 4

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Background

The problem originates in a question posed by Esther Klein in 1932; the resulting paper by Erdős and Szekeres led to Szekeres and Klein's marriage, hence Erdős's name for it, the happy ending problem.

Known partial results

  • Known exactly for n≤6n \le 6; ES(6)=17\mathrm{ES}(6) = 17 was established by Szekeres and Peters in 2006 with a computer search.
  • Lower bound 2n−2+12^{n-2}+1 from an explicit construction of Erdős and Szekeres.
  • Suk (2017) proved ES(n)≤2n+o(n)\mathrm{ES}(n) \le 2^{n + o(n)}, closing the gap to a subexponential factor after eight decades of small improvements.
  • n=7n = 7 is the first unknown case and is a finite, fully specified search problem.
References
  1. [1]A. Suk, On the Erdős–Szekeres convex polygon problem, J. Amer. Math. Soc. 30 (2017), 1047–1053. link

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