Jun Ma and Lin's enumeration conjecture for inversion sequences avoiding 0012

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Let In(0012)\mathbf I_n(0012) denote the set of inversion sequences of length nn avoiding the pattern 00120012. Jun Ma and Lin's conjecture. For n≥1n\geq 1, we have

∣In(0012)∣=1+∑i=1n−1(2ii−1).|\mathbf I_n(0012)|=1+\sum_{i=1}^{n-1}{2i\choose i-1}.

In other words, the unbalanced Wilf-equivalence

(0012)∼(021,120)(0012)\thicksim(021,120)

holds. The source presents this as a conjectured enumeration related to OEIS sequence A279561 and gives no indication that it has been resolved.

References

Primary source

Chunyan Yan and Zhicong Lin, “Inversion sequences avoiding pairs of patterns”, arXiv:1912.03674 (2020).

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