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FixedPoints ​

The number of fixed points of : positions with .

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FixedPoints(p)the fixed-point count of a one-line permutation

Domain: Permutation statistics

Details
  • A permutation with no fixed points is a derangement (see Derangements)
  • Averaged over the count is exactly , independent of

Examples

See also: Derangements, CycleCount, SymmetricGroup