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arXiv · 2607.10978

A tight single-change covering design with block size 6

Richard Bean
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Abstract

We give a tight single-change covering design with $v=26$ and $k=6$. This answers Problem 1 of the Nineteenth British Combinatorial Conference, which asked whether such a design exists with block size greater than $5$. We also describe the satisfiability search that found the design, including negative search results at the smallest admissible order $v=21$.

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Richard Bean. 2026-07-13. A tight single-change covering design with block size 6. https://arxiv.org/abs/2607.10978

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