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arXiv · 2205.06004

Paths through equally spaced points on a circle

Brendan D. McKay·Tim Peters
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Abstract

Consider $n$ points evenly spaced on a circle, and a path of $n-1$ chords that uses each point once. There are $m=\lfloor n/2\rfloor$ possible chord lengths, so the path defines a multiset of $n-1$ elements drawn from $\{1,2,\ldots,m\}$. The first problem we consider is to characterize the multisets which are realized by some path. Buratti conjectured that all multisets can be realized when $n$ is prime, and a generalized conjecture for all $n$ was proposed by Horak and Rosa. Previously the conjecture was proved for $n \leq 19$ and $n=23$; we extend this to $n\leq 37$ (OEIS sequence A352568). The second problem is to determine the number of distinct (euclidean) path lengths that can be realized. For this there is no conjecture; we extend current knowledge from $n\leq 16$ to $n\leq 37$ (OEIS sequence A030077). When $n$ is prime, twice a prime, or a power of 2, we prove that two paths have the same length only if they have the same multiset of chord lengths.

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Brendan D. McKay, Tim Peters. 2022-05-12. Paths through equally spaced points on a circle. https://arxiv.org/abs/2205.06004

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