Bijection between constrained Delannoy paths and Catalan paths avoiding symmetric peaks

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For a positive integer nn, let EPn,n(1)(NE,EN)E\mathcal{P}^{(1)}_{n,n}(NE,EN) be the set of Delannoy paths from (0,0)(0,0) to (n,n)(n,n) consisting of north-steps N=(0,1)N=(0,1), east-steps E=(1,0)E=(1,0), and diagonal-steps D=(1,1)D=(1,1) that avoid the patterns NENE and ENEN, end with an east step EE, and are not below y=xy=x. Let the second set consist of Catalan paths of size n+1n+1 avoiding symmetric peaks, where a symmetric peak is a peak whose maximal mountain has the form NiEiN^iE^i.

Delannoy–Catalan bijection conjecture. For every positive integer nn, there exists a bijection between EPn,n(1)(NE,EN)E\mathcal{P}^{(1)}_{n,n}(NE,EN) and the set of Catalan paths of size n+1n+1 avoiding symmetric peaks.

This conjecture proposes a direct combinatorial correspondence between a class of constrained Delannoy paths and Catalan paths with a local peak-avoidance condition. The surrounding discussion identifies the related generating-function identity, but the supplied text gives no evidence that this bijection has been proved or disproved.

References

Primary source

Seunghyun Seo and Heesung Shin, “On Delannoy paths without peaks and valleys”, arXiv:2203.07770 (2022).

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