Conjecture on 0012-avoiding ascent sequences and Catalan bistatistics

From papers

Let S0012(n){\mathcal S}_{0012}(n) be the set of ascent sequences of length nn avoiding 00120012, let A0012(n)=S0012(n)A_{0012}(n)=|{\mathcal S}_{0012}(n)|, let fwd\operatorname{fwd} be the length of the maximal final weakly decreasing sequence, and let zeros\operatorname{zeros} count zero entries. The 0012 Catalan-bistatistic conjecture. One has A0012(n)=CnA_{0012}(n)=C_n, the nn-th Catalan number; (asc,fwd)(\operatorname{asc},\operatorname{fwd}) on S0012(n){\mathcal S}_{0012}(n) has the same distribution as (asc,RLmax)(\operatorname{asc},\operatorname{RLmax}) on 132-avoiding permutations; consequently ascents have the Narayana distribution on S0012(n){\mathcal S}_{0012}(n); and (asc,fwd)(\operatorname{asc},\operatorname{fwd}) and (asc,zeros)(\operatorname{asc},\operatorname{zeros}) have the same distribution on 0012-avoiding ascent sequences. The source treats these enumerative and distributional identities as conjectural and gives no resolution.

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Sources & referencesView supporting material

Primary source

Paul Duncan and Einar Steingrimsson, “Pattern avoidance in ascent sequences”, arXiv:1109.3641 (2011).

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