Identifier
- St001061: Permutations ⟶ ℤ
Values
[1,2] => 0
[2,1] => 1
[1,2,3] => 0
[1,3,2] => 1
[2,1,3] => 1
[2,3,1] => 0
[3,1,2] => 0
[3,2,1] => 2
[1,2,3,4] => 0
[1,2,4,3] => 1
[1,3,2,4] => 1
[1,3,4,2] => 0
[1,4,2,3] => 0
[1,4,3,2] => 2
[2,1,3,4] => 1
[2,1,4,3] => 2
[2,3,1,4] => 0
[2,3,4,1] => 0
[2,4,1,3] => 0
[2,4,3,1] => 1
[3,1,2,4] => 0
[3,1,4,2] => 0
[3,2,1,4] => 2
[3,2,4,1] => 1
[3,4,1,2] => 1
[3,4,2,1] => 1
[4,1,2,3] => 0
[4,1,3,2] => 1
[4,2,1,3] => 1
[4,2,3,1] => 2
[4,3,1,2] => 1
[4,3,2,1] => 3
[1,2,3,4,5] => 0
[1,2,3,5,4] => 1
[1,2,4,3,5] => 1
[1,2,4,5,3] => 0
[1,2,5,3,4] => 0
[1,2,5,4,3] => 2
[1,3,2,4,5] => 1
[1,3,2,5,4] => 2
[1,3,4,2,5] => 0
[1,3,4,5,2] => 0
[1,3,5,2,4] => 0
[1,3,5,4,2] => 1
[1,4,2,3,5] => 0
[1,4,2,5,3] => 0
[1,4,3,2,5] => 2
[1,4,3,5,2] => 1
[1,4,5,2,3] => 1
[1,4,5,3,2] => 1
[1,5,2,3,4] => 0
[1,5,2,4,3] => 1
[1,5,3,2,4] => 1
[1,5,3,4,2] => 2
[1,5,4,2,3] => 1
[1,5,4,3,2] => 3
[2,1,3,4,5] => 1
[2,1,3,5,4] => 2
[2,1,4,3,5] => 2
[2,1,4,5,3] => 1
[2,1,5,3,4] => 1
[2,1,5,4,3] => 3
[2,3,1,4,5] => 0
[2,3,1,5,4] => 1
[2,3,4,1,5] => 0
[2,3,4,5,1] => 0
[2,3,5,1,4] => 0
[2,3,5,4,1] => 1
[2,4,1,3,5] => 0
[2,4,1,5,3] => 0
[2,4,3,1,5] => 1
[2,4,3,5,1] => 0
[2,4,5,1,3] => 1
[2,4,5,3,1] => 1
[2,5,1,3,4] => 0
[2,5,1,4,3] => 1
[2,5,3,1,4] => 0
[2,5,3,4,1] => 1
[2,5,4,1,3] => 1
[2,5,4,3,1] => 2
[3,1,2,4,5] => 0
[3,1,2,5,4] => 1
[3,1,4,2,5] => 0
[3,1,4,5,2] => 0
[3,1,5,2,4] => 0
[3,1,5,4,2] => 1
[3,2,1,4,5] => 2
[3,2,1,5,4] => 3
[3,2,4,1,5] => 1
[3,2,4,5,1] => 1
[3,2,5,1,4] => 1
[3,2,5,4,1] => 2
[3,4,1,2,5] => 1
[3,4,1,5,2] => 1
[3,4,2,1,5] => 1
[3,4,2,5,1] => 1
[3,4,5,1,2] => 0
[3,4,5,2,1] => 0
[3,5,1,2,4] => 1
[3,5,1,4,2] => 2
[3,5,2,1,4] => 1
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Description
The number of indices that are both descents and recoils of a permutation.
Code
def statistic(pi):
return len( set(pi.descents()).intersection(pi.inverse().descents()))
Created
Dec 21, 2017 at 08:47 by Christian Stump
Updated
Dec 21, 2017 at 08:47 by Christian Stump
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