Erdős problem #396

For each integer k1k\ge 1, determine the smallest integer nkn\ge k such that n(n1)(n2)(nk)n(n-1)(n-2)\cdots(n-k) divides the central binomial coefficient (2nn)\binom{2n}{n}; equivalently, determine nk=min{nZk:j=0k(nj)(2nn)}n_k=\min\{n\in\mathbb{Z}_{\ge k}:\prod_{j=0}^{k}(n-j)\mid\binom{2n}{n}\} whenever this set is nonempty.

Progress summary

Partially solved

A new computation records the smallest known examples in a finite range, but it does not settle the general Erdős problem.

Erdős problem #396 is a named Erdős question whose general resolution remains open. The latest development is a computational record of smallest witnesses for k=8,,13k=8,\ldots,13.

August 2026 finite-range computation

The project supplies data for future general arguments, but explicitly does not resolve the problem beyond the tested finite range.

Current status (as of August 2026): Finite-range computational data are available for k=8,,13k=8,\ldots,13, while the general Erdős problem remains open.

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Primary source

GitHub

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Solutions 0

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