A Partial Answer to Propp's Problem 7 on Benzel Tilings: An Infinite Family of Type-103 Tilings and the Open Cases with |a−b| ≤ 7 or max(a,b) ≤ 60
Manuscript 19 October 2026 · Online 19 October 2026
Abstract
Propp asked whether every \((a,b)\)-benzel with nonnegative Conway–Lagarias invariant has a tiling by right-pointing stones and bones of all three orientations, a tiling of type 103 (Problem 7 of his list of twenty problems). By published theorems of Defant, Li, Propp and Young, of Defant, Foster, Li, Propp and Young, and of Kim and Propp, the question is open only for the benzels \((d+3J,\,2d+3J)\) with \(d\ge3\) and \(1\le J\le\frac{(d-2)(d+1)}2\) and for their mirror images. We give a partial answer; Problem 7 remains open in general. We prove that for every \(D\ge2\) the \((4D-3,\,5D-3)\)-benzel has a type-103 tiling, formed by a central triangle of \(\frac{(D-1)(D-2)}2\) right stones and three congruent sectors, each tiled by parallel bones; for \(D\ge3\) these benzels lie in the open region. We also verify the question, by computer, for every open case with \(|a-b|\le7\) and for every open case with \(\max(a,b)\le60\): for each of these benzels a tiling is stored and checked by a short self-contained program. This is a finite verification and says nothing about larger cases. The row \((n,2n-3)\) and the window \(\max(a,b)\le14\) are covered by unrefereed preprints of 2026 (by A. C. Li and by The Clankers), which we credit and do not use. We also record computational evidence that the simplest ring inductions, which add a ring around a smaller benzel, do not reach the cases near the line where the invariant vanishes. This is an unrefereed note.
Record
- Affiliation
- Mercury Software GmbH
- Contact
- [email protected] · GitHub
- Result
- Partial answer: an infinite family and all open cases up to max(a,b) = 60
- Categories
- math.CO
- Manuscript
- 19 October 2026
- Online release
- 19 October 2026
- Version
- 1.0
- License
- Creative Commons Attribution 4.0 International
Files and verification
The PDF is the canonical reading copy. The source archive contains the LaTeX manuscript, bibliography, reproducibility material, and audit documents without build artefacts.
Citation
Alper Ferudun, “A Partial Answer to Propp's Problem 7 on Benzel Tilings: An Infinite Family of Type-103 Tilings and the Open Cases with |a−b| ≤ 7 or max(a,b) ≤ 60,” EulerSolve Research Papers, AMR-123-0003, 2026. https://doi.org/10.5281/zenodo.23483633.
BibTeX
@misc{Ferudun2026Amr1230003,
author = {Ferudun, Alper},
title = {A Partial Answer to Propp's Problem 7 on Benzel Tilings: An Infinite Family of Type-103 Tilings and the Open Cases with |a−b| ≤ 7 or max(a,b) ≤ 60},
year = {2026},
howpublished = {EulerSolve Research Papers},
url = {https://eulersolve.org/papers/amr-123-0003/},
doi = {10.5281/zenodo.23483633},
note = {AMR-123-0003; unrefereed preprint}
}