Chord Diagrams for Motzkin Numbers
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This Demonstration illustrates one of the many interpretations of the Motzkin numbers: Given points arranged around a circle, the Motzkin numbers count the number of ways to draw from zero to nonintersecting chords.
Contributed by: Robert Dickau (April 2011)
Open content licensed under CC BY-NC-SA
 R. P. Stanley, Enumerative Combinatorics, Volume 2, Cambridge: Cambridge University Press, 1999 p. 238.
"Chord Diagrams for Motzkin Numbers"
Wolfram Demonstrations Project
Published: April 27 2011