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Combinatorics

The Harary–Hill and Zarankiewicz crossing-number formulas

OpenAI research collection · 2 manuscripts · Source checked 2026-10-19

OpenAI's result summary

Resolves the Harary–Hill conjecture and Turán's brickyard problem in the Zarankiewicz formulation, determining the crossing numbers of every complete and complete bipartite graph. The result proves the optimality of the classical drawings among all plane drawings with continuous edge arcs.

Read the manuscripts

Short excerpts below come from OpenAI's abstracts. The full abstract and original PDF preserve the paper's precise scope.

MANUSCRIPT 01

The crossing number of complete graphs

We prove the Harary–Hill conjecture: for every positive integer n, the ordinary crossing number of the complete graph K_(n) is \displaystyle \frac14\lfloor\frac n2\rfloor \lfloor\frac{n-1}{2}\rfloor \lfloor\frac{n-2}{2}\rfloor \lfloor\frac{n-3}{2}\rfloor.

This PDF is listed in OpenAI's formalization catalogue. See the scope and dependencies before interpreting coverage.

MANUSCRIPT 02

The crossing number of complete bipartite graphs

We prove the Zarankiewicz crossing-number conjecture, resolving Turán's brickyard problem. For all positive integers m, n, the ordinary crossing number of the complete bipartite graph K_{m,n} is \displaystyle \lfloor\frac m2\rfloor \lfloor\frac{m-1}{2}\rfloor \lfloor\frac n2\rfloor \lfloor\frac{n-1}{2}\rfloor.

This PDF is listed in OpenAI's formalization catalogue. See the scope and dependencies before interpreting coverage.

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