Generating Functions for Domino Matchings in the 2 × k Game of Memory
Donovan Young
St Albans, Hertfordshire AL1 4SZ
United Kingdom
Abstract:
When all the elements of the multiset {1, 1, 2, 2, 3, 3,..., k,
k} are placed in the cells of a 2 × k rectangular array,
in how many configurations are exactly v of the pairs directly
over top one another, and exactly h directly beside one another --
thus forming 1 × 2 or 2 × 1 dominoes? We consider the
sum of matching numbers over the graphs obtained by deleting h
horizontal and v vertical vertex pairs from the 2 × k
grid graph in all possible ways, providing a generating function for
these aggregate matching polynomials. We use this result to derive a
formal generating function enumerating the domino matchings, making
connections with linear chord diagrams.
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(Concerned with sequences
A000045
A001883
A046741
A055140
A079267
A178523
A265167
A318243
A318244
A318267
A318268
A318269
A318270
A325753
A325754.)
Received June 8 2019; revised versions received July 31 2019; December 18 2019.
Published in Journal of Integer Sequences,
December 27 2019.
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