Regular Article
Twelve Countings with Rooted Plane Trees

https://doi.org/10.1006/eujc.1995.0095Get rights and content
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Abstract

The average numbers of (1) antichains, (2) maximal antichains, (3) chains, (4) infima closed sets, (5) connected sets, (6) independent sets, (7) maximal independent sets, (8) brooms, (9) matchings, (10) maximal matchings, (11) linear extensions and (12) drawings in (of) a rooted plane tree onnvertices are investigated. Using generating functions we determine the asymptotics and give some explicit formulae and identities. In conclusion, we discuss the extremal values of the above quantitites and pose some problems.

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