English

Paths through equally spaced points on a circle

Combinatorics 2022-09-14 v3

Abstract

Consider nn points evenly spaced on a circle, and a path of n1n-1 chords that uses each point once. There are m=n/2m=\lfloor n/2\rfloor possible chord lengths, so the path defines a multiset of n1n-1 elements drawn from {1,2,,m}\{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 nn is prime, and a generalized conjecture for all nn was proposed by Horak and Rosa. Previously the conjecture was proved for n19n \leq 19 and n=23n=23; we extend this to n37n\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 n16n\leq 16 to n37n\leq 37 (OEIS sequence A030077). When nn 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.

Keywords

Cite

@article{arxiv.2205.06004,
  title  = {Paths through equally spaced points on a circle},
  author = {Brendan D. McKay and Tim Peters},
  journal= {arXiv preprint arXiv:2205.06004},
  year   = {2022}
}

Comments

Additional citations, accepted by Journal of Integer Sequences

R2 v1 2026-06-24T11:15:19.128Z