The Desbot-Wilf classification conjecture for patterns in S_4

Let S4S_4 be the set of permutations of length 44. For a permutation τ\tau, define its descent bottom set by

Desbot(τ)={τ(i+1)τ(i)>τ(i+1)}.\operatorname{Desbot}(\tau)=\{\tau(i+1)\mid \tau(i)>\tau(i+1)\}.

Two patterns are Desbot-Wilf equivalent if their avoidance classes have the same Desbot\operatorname{Desbot}-distribution for every permutation length. The Desbot-Wilf classification conjecture. The non-singleton Desbot\operatorname{Desbot}-Wilf equivalence classes in S4S_4 are

{2134,3412},{2314,2413},{2143,4312},\{2134,3412\},\quad \{2314,2413\},\quad \{2143,4312\}, {1423,1342},{3142,3241,4132,4213}.\{1423,1342\},\quad \{3142,3241,4132,4213\}.

This is presented as equivalent to the preceding Destop classification by reverse complement; its general status is unresolved in the supplied text.

Sources & referencesView supporting material

Primary source

Alexander Burstein, “Distribution of sets of descent tops and descent bottoms on restricted permutations”, arXiv:2306.08065 (2025).

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