Catalan number

English Etymology Named after the Belgian mathematician Eugène Catalan (1814–1894). Noun In combinatorial mathematics, any of a sequence of natural numbers that occur in various counting problems, often involving recursively defined objects; the nth Catalan number is equal to (2n choose n) over (n+1). en 1998-07-29 Michael Collins A CONTEXT-FREE GRAMMAR FOR ENGLISH http://old-site.clsp.jhu.edu/ws98/projects/nlp/ http://old-site.clsp.jhu.edu/ws98/projects/nlp/doc/9801/l1.ps 2013-04-19 AMBIGUITY LEADS TO AN EXPONENTIAL NUMBER OF TREESI saw the man with the telescope on the box in the car under the table ...n prepositional phrases ⇒ (n + 1)’th catalan number Cn — the nth Catalan number — could be described as the number of distinct ways in which a sequence of n + 1 numbers could be associated by means of some specified binary operator. en eponyms en Combinatorics