Godbole–Goyt–Herdan–Pudwell recurrence conjecture for ordered partitions with blocks of size 2

An ordered partition of [2k][2k] with kk blocks of size 22 is counted by op[2k](123)op_{[2^k]}(123) when it avoids the permutation pattern 123123. Godbole–Goyt–Herdan–Pudwell's recurrence conjecture. For k0k\geq0,

op[2k+2](123)=329k3+1215k2+1426k+5282(k+2)(2k+5)(7k+5)op[2k+1](123)+3(k+1)(2k+1)(7k+12)(k+2)(2k+5)(7k+5)op[2k](123).op_{[2^{k+2}]}(123)= \frac{329k^3+1215k^2+1426k+528}{2(k+2)(2k+5)(7k+5)}op_{[2^{k+1}]}(123)+\frac{3(k+1)(2k+1)(7k+12)}{(k+2)(2k+5)(7k+5)}op_{[2^k]}(123).

This conjecture arose from computer-generated recurrence discovery using Zeilberger's Maple package FindRecFindRec and gives a second-order linear recurrence for the enumeration of 123123-avoiding ordered partitions with all blocks of size 22.

Sources & referencesView supporting material

Primary source

William Y. C. Chen, Alvin Y. L. Dai and Robin D. P. Zhou, “Ordered Partitions Avoiding a Permutation of Length 3”, arXiv:1304.3187 (2013).

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