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Catalan number

File:Noncrossing_partitions_5.svg · Wikimedia Commons · See Wikimedia Commons

EntityQ270513· pop 42· linked from 310 articles

Catalan number

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Also known as Segner number

recursive integer sequence

Wikidata facts

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Catalan 4 leaves binary tree example.svg
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time of discovery or invention
1800-00-00
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Catalan numbers
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The C5 = 42 noncrossing partitions of a 5-element set (below, the other 10 of the 52 partitions) The Catalan numbers are a sequence of natural numbers that occur in various counting problems, often involving recursively defined objects. They are named after Eugène Catalan, though they were previously discovered in the 1730s by Minggatu.

The n-th Catalan number can be expressed directly in terms of the central binomial coefficients by

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