Explicit generating-function form conjecture for even and odd 132-occurrence counts

From papers

Let Er(x)E_r(x) and Or(x)O_r(x) denote the generating functions for even and odd permutations, respectively, with exactly rr occurrences of 132132. For every r1r\geq1, there exist polynomials Ar(x)A_r(x), Br(x)B_r(x), Cr(x)C_r(x), and Dr(x)D_r(x) with integer coefficients such that

Er(x)=14(Ar(x)+Br(x))+14Cr(x)(14x)r+1/2+14Dr(x)(14x2)r+1/2,Or(x)=14(Ar(x)Br(x))+14Cr(x)(14x)r+1/214Dr(x)(14x2)r+1/2.\begin{aligned} E_r(x)&=\frac{1}{4}(A_r(x)+B_r(x))+\frac{1}{4}C_r(x)(1-4x)^{-r+1/2}+\frac{1}{4}D_r(x)(1-4x^2)^{-r+1/2},\\ O_r(x)&=\frac{1}{4}(A_r(x)-B_r(x))+\frac{1}{4}C_r(x)(1-4x)^{-r+1/2}-\frac{1}{4}D_r(x)(1-4x^2)^{-r+1/2}. \end{aligned}

Explicit generating-function form conjecture. The displayed representations hold for every r1r\geq1. The paper presents this as a stronger conjecture motivated by explicit results; no proof or disproof is supplied in the given text.

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Sources & referencesView supporting material

Primary source

T. Mansour, “Counting occurrences of 132 in an even permutation”, arXiv:math/0211205 (2002).

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