English

The Kolakoski sequence and related conjectures about orbits

Combinatorics 2017-03-02 v2

Abstract

The Kolakoski sequence is the unique infinite sequence with values in {1,2}\{1, 2\} and first term twems 1,2,1, 2, \ldots which equals the sequence of run-lengths of itself, we call this K(1,2).K(1, 2). We define K(m,n)K(m, n) similarly for m+nm+n odd. A well-known open problem is that its limiting density is one-half. Indeed, not much is known about the Kolakoski sequence. The focus of this paper in on conjectures related to the Kolakoski sequence which are more discrete in nature. We conjecture that a certain doubly infinite family of finite sequences E1,n(12j,12j)E_{1, n}\left(1^{2^j}, 1^{2j}\right) has odd length for all j>0j>0 and even n>0.n>0. We define cf(m,n,d)cf(m, n, d) to be the "correlation frequency" or limiting probability that terms in K(m,n)K(m, n) which are dd apart are equal. We conjecture that the sign of cf(m,n,d)1/2cf(m, n, d) - 1/2 is periodic mod m+n.m+n. We also discuss extensive empirical evidence for these conjectures.

Keywords

Cite

@article{arxiv.1702.08156,
  title  = {The Kolakoski sequence and related conjectures about orbits},
  author = {Bobby Shen},
  journal= {arXiv preprint arXiv:1702.08156},
  year   = {2017}
}

Comments

9 pages, draft, provisional title

R2 v1 2026-06-22T18:29:03.667Z