Stuttering Conway Sequences Are Still Conway Sequences
Abstract
A look-and-say sequence is obtained iteratively by reading off the digits of the current value, grouping identical digits together: starting with 1, the sequence reads: 1, 11, 21, 1211, 111221, 312211, etc. (OEIS A005150). Starting with any digit gives Conway's sequence: , , , , , etc. (OEIS A006715). Conway popularised these sequences and studied some of their properties. In this paper we consider a variant subbed "look-and-say again" where digits are repeated twice. We prove that the look-and-say again sequence contains only the digits , where represents the starting digit. Such sequences decompose and the ratio of successive lengths converges to Conway's constant. In fact, these properties result from a commuting diagram between look-and-say again sequences and "classical" look-and-say sequences. Similar results apply to the "look-and-say three times" sequence.
Cite
@article{arxiv.2006.06837,
title = {Stuttering Conway Sequences Are Still Conway Sequences},
author = {Éric Brier and Rémi Géraud-Stewart and David Naccache and Alessandro Pacco and Emanuele Troiani},
journal= {arXiv preprint arXiv:2006.06837},
year = {2020}
}