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Almost Golomb Sequences

Number Theory 2026-04-06 v1 Combinatorics

Abstract

Golomb's sequence is the unique nondecreasing sequence of positive integers in which each nn appears exactly a(n)a(n) times. It satisfies the global self-referential rule a(a(n)+a(n1)++a(1))=n, a\bigl(a(n)+a(n-1)+\cdots+a(1)\bigr)=n, grows smoothly like a power of nn governed by the golden ratio, and is not kk-regular for any k2k\ge 2. We introduce almost Golomb sequences, obtained by truncating the cumulative sum to a sliding window of fixed size rr, a(a(n)+a(n1)++a(nr+1))=n. a\bigl(a(n)+a(n-1)+\cdots+a(n-r+1)\bigr)=n. This finite-memory truncation changes the nature of the sequence completely. The smooth power law gives way to oscillatory linear growth, and the sequence becomes rr-regular for every r2r\ge 2. For small values of rr we establish explicit denesting formulas, prove that a(n)/na(n)/n does not converge, and uncover combinatorial structure including a cellular automaton and a palindromic substitution. A numerical surprise emerges when one varies rr. The maximum multiplicity across the family of sequences is governed by Golomb's sequence itself. The sequence that was truncated reappears as the law controlling the family it generated.

Keywords

Cite

@article{arxiv.2604.02404,
  title  = {Almost Golomb Sequences},
  author = {Benoit Cloitre},
  journal= {arXiv preprint arXiv:2604.02404},
  year   = {2026}
}

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41 pages, 1 table