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OP-6999OpenCombinatorics

Zero density in the easily bored sequence

TheoremDB P2880 · combinatorics on words

Inferred from the community field; finer classification has not been reviewed.

Source catalogue assessmentAs of 2026-09-08Source & evidence ↓

Problem statement

For a finite binary word ww and x∈{0,1}x\in\{0,1\}, let rw(x)r_w(x) be the largest integer r≥1r\ge 1 for which wxwx ends in uru^r for some nonempty word uu, and let ℓw(x)\ell_w(x) be the largest length ∣u∣|u| among witnesses for that maximal rr. Define b1=0b_1=0; for m≥2m\ge 2, let bmb_m be the bit xx that minimizes (rb1⋯bm−1(x),ℓb1⋯bm−1(x))(r_{b_1\cdots b_{m-1}}(x),\ell_{b_1\cdots b_{m-1}}(x)) in lexicographic order. Does the limit lim⁡N→∞N−1∣{1≤m≤N:bm=0}∣\lim_{N\to\infty}N^{-1}|\{1\le m\le N:b_m=0\}| exist and equal 1/21/2?

Lean 4

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Background

Additional formulation recorded by the source

For the displayed greedy binary sequence b, decide whether lim_{N->infinity} (1/N) sum_{m=1}^N 1[b_m=0] = 1/2.

Progress & source assessment

Source-reported assessment, retrieved 8 September 2026. Frontier Science has not independently reviewed this status.

Open. No signed Lean verification is attached to this problem or its selected resolution.

References
  1. [1]TheoremDB P2880 link

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