Front crossing–nesting symmetry conjecture for set partitions

Let Πn\Pi_n be the set of set partitions of [n][n], and let FCR(π)\operatorname{FCR}(\pi) and FNE(π)\operatorname{FNE}(\pi) denote respectively the front crossing and front nesting statistics of π\pi. Front crossing–nesting symmetry conjecture. For every nn,

πΠnxFCR(π)yFNE(π)=πΠnxFNE(π)yFCR(π).\sum_{\pi\in\Pi_n} x^{\operatorname{FCR}(\pi)} y^{\operatorname{FNE}(\pi)}= \sum_{\pi\in\Pi_n} x^{\operatorname{FNE}(\pi)} y^{\operatorname{FCR}(\pi)}.

The conjecture asserts that the joint distribution of the front crossing and front nesting statistics is symmetric; it had been checked up to n=11n=11 in the source, with no resolution supplied there.

Sources & referencesView supporting material

Primary source

Jang Soo Kim, “Front representation of set partitions”, arXiv:0907.1485 (2011).

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