Catalan number

Etymology
Named after the Belgian mathematician Eugène Catalan (1814–1894).

Noun

 * 1) 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).
 * 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.
 * 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.