Shape-Wilf equivalence through length eight

We determine the shape-Wilf-equivalence classes of single permutation patterns at lengths seven and eight. The known Backelin-West-Xin and Stankova-West equivalences, with right direct-sum extension, generate 4,862 and 39,326 components, respectively, and the retained separation certificates distinguish all of them. The paper proves a forest formula for the number of generated components, gives exact counting algorithms and fiber-cancellation arguments, and includes all final separation rows. Independent decisive recounts validate all 94 length-seven order-13 values and the required length-eight order-15 layers and finite cutoff premises. Full-root reconstructions retain the certified ordinary-Wilf atlas and independent earlier board arrays as explicit dependencies. The archive supplies sources, raw outputs, controls, acceptance reviews, and a portable retained-data verifier. The all-length classification question remains open.

Authors

Publication Details

Journal
Zenodo (CERN European Organization for Nuclear Research)
Published
2026-11-05
DOI
https://doi.org/10.5281/zenodo.23990869
Primary Topic
Advanced Combinatorial Mathematics
Type
preprint
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preprint

Shape-Wilf equivalence through length eight

Eric Cowan
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Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
preprint

Shape-Wilf equivalence through length eight

Eric Cowan
preprint en

Abstract

We determine the shape-Wilf-equivalence classes of single permutation patterns at lengths seven and eight. The known Backelin-West-Xin and Stankova-West equivalences, with right direct-sum extension, generate 4,862 and 39,326 components, respectively, and the retained separation certificates distinguish all of them. The paper proves a forest formula for the number of generated components, gives exact counting algorithms and fiber-cancellation arguments, and includes all final separation rows. Independent decisive recounts validate all 94 length-seven order-13 values and the required length-eight order-15 layers and finite cutoff premises. Full-root reconstructions retain the certified ordinary-Wilf atlas and independent earlier board arrays as explicit dependencies. The archive supplies sources, raw outputs, controls, acceptance reviews, and a portable retained-data verifier. The all-length classification question remains open.

Zenodo (CERN European Organization for Nuclear Research)
Advanced Combinatorial Mathematics
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