Difference between revisions of "Derangement"
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| − | A '''derangement''' is a [[permutation]] with no [[fixed point]]s. | + | A '''derangement''' is a [[permutation]] with no [[fixed point]]s. A derangement can also be thought of as a permutation in which none of the objects are in their original space. For example, the derangements of <math>(1,2,3)</math> are <math>(2, 3, 1)</math> and <math>(3, 1, 2)</math>. The number of derangements of a set of x objects is denoted !x, and is given by the formula: |
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| + | <math>\displaystyle !x = x! \sum_{k=1}^{n} \frac{-1^k}{k!}</math> | ||
{{stub}} | {{stub}} | ||
Revision as of 16:14, 13 November 2006
A derangement is a permutation with no fixed points. A derangement can also be thought of as a permutation in which none of the objects are in their original space. For example, the derangements of 
are 
and 
. The number of derangements of a set of x objects is denoted !x, and is given by the formula:
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