Linear k-Chord Diagrams
Donovan Young
St Albans, Hertfordshire AL1 4SZ
United Kingdom
Abstract:
We generalize the notion of linear chord diagrams to the case of matched
sets of size k, which we call k-chord diagrams. We provide
formal generating functions and recurrence relations enumerating these
k-chord diagrams by the number of short chords, where the latter
is defined as all members of the matched set being adjacent, and is the
generalization of a short chord or loop in a linear chord diagram. We
also enumerate k-chord diagrams by the number of connected
components built from short chords and provide the associated generating
functions in this case. We show that the distributions of short chords
and connected components are asymptotically Poisson, and provide the
associated means. Finally, we provide recurrence relations enumerating
non-crossing k-chord diagrams by the number of short chords,
generalising the Narayana numbers, and establish asymptotic normality,
providing the associated means and variances. Applications to generalized
games of memory are also discussed.
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(Concerned with sequences
A062993
A091320
A334056
A334057
A334058
A334059
A334060
A334061
A334062
A334063.)
Received August 11 2020; revised versions received August 12 2020; September 29 2020.
Published in Journal of Integer Sequences,
October 13 2020.
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