Entringer number conjecture for 000-avoiding inversion sequences

The Entringer numbers dn,kd_{n,k} count down/up permutations of [n+1][n+1] whose first entry is k+1k+1, and satisfy

dn,k=dn,k1+dn1,nk.d_{n,k}=d_{n,k-1}+d_{n-1,n-k}.

An Entringer number conjecture asserts that, for n1n\geq 1 and 0kn10\leq k\leq n-1, dn,kd_{n,k} is the number of inversion sequences eIn(000)e\in\mathbf{I}_n(000) with last entry en=k1e_n=k-1.

This conjecture proposes a direct interpretation of the Entringer numbers in terms of 000-avoiding inversion sequences; the source reports it as suggested by computations, and no resolution is provided.

Sources & referencesView supporting material

Primary source

Sylvie Corteel, Megan A. Martinez, Carla D. Savage and Michael Weselcouch, “Patterns in Inversion Sequences I”, arXiv:1510.05434 (2016).

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