Journal of Integer Sequences, Vol. 23 (2020), Article 20.9.1

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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