# Descent

Revision as of 19:14, 6 August 2009 by JBL (talk | contribs) (Created page with 'Given a permutation <math>w = w_1 w_2 \cdots w_n)</math> of <math>\{1, 2, \ldots, n\}</math>, <math>w</math> is said to have a '''descent''' at position <math>i</math> if and…')

Given a permutation of , is said to have a **descent** at position if and only if . For example, the permutation has descents at positions 2 (since ) and 4 (since ).

The set of descents of a permutation is called its *descent set.* If is a permutation of then its descent set is some subset of .

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