English

Repetition avoidance in products of factors

Discrete Mathematics 2019-04-30 v2 Combinatorics

Abstract

We consider a variation on a classical avoidance problem from combinatorics on words that has been introduced by Mousavi and Shallit at DLT 2013. Let pexpi(w)\texttt{pexp}_i(w) be the supremum of the exponent over the products of ii factors of the word ww. The repetition threshold RTi(k)\texttt{RT}_i(k) is then the infimum of pexpi(w)\texttt{pexp}_i(w) over all words wΣkωw\in\Sigma^\omega_k. Mousavi and Shallit obtained that RTi(2)=2i\texttt{RT}_i(2)=2i and RT2(3)=134\texttt{RT}_2(3)=\tfrac{13}4. We show that RTi(3)=3i2+14\texttt{RT}_i(3)=\tfrac{3i}2+\tfrac14 if ii is even and RTi(3)=3i2+16\texttt{RT}_i(3)=\tfrac{3i}2+\tfrac16 if ii is odd and i3i\ge3.

Keywords

Cite

@article{arxiv.1809.01426,
  title  = {Repetition avoidance in products of factors},
  author = {Pamela Fleischmann and Pascal Ochem and Kamellia Reshadi},
  journal= {arXiv preprint arXiv:1809.01426},
  year   = {2019}
}