Identifier
- St001726: Permutations ⟶ ℤ
Values
[1] => 0
[1,2] => 0
[2,1] => 1
[1,2,3] => 0
[1,3,2] => 1
[2,1,3] => 1
[2,3,1] => 2
[3,1,2] => 1
[3,2,1] => 2
[1,2,3,4] => 0
[1,2,4,3] => 1
[1,3,2,4] => 1
[1,3,4,2] => 2
[1,4,2,3] => 1
[1,4,3,2] => 2
[2,1,3,4] => 1
[2,1,4,3] => 2
[2,3,1,4] => 2
[2,3,4,1] => 3
[2,4,1,3] => 2
[2,4,3,1] => 3
[3,1,2,4] => 1
[3,1,4,2] => 2
[3,2,1,4] => 2
[3,2,4,1] => 3
[3,4,1,2] => 3
[3,4,2,1] => 4
[4,1,2,3] => 1
[4,1,3,2] => 2
[4,2,1,3] => 2
[4,2,3,1] => 3
[4,3,1,2] => 3
[4,3,2,1] => 4
[1,2,3,4,5] => 0
[1,2,3,5,4] => 1
[1,2,4,3,5] => 1
[1,2,4,5,3] => 2
[1,2,5,3,4] => 1
[1,2,5,4,3] => 2
[1,3,2,4,5] => 1
[1,3,2,5,4] => 2
[1,3,4,2,5] => 2
[1,3,4,5,2] => 3
[1,3,5,2,4] => 2
[1,3,5,4,2] => 3
[1,4,2,3,5] => 1
[1,4,2,5,3] => 2
[1,4,3,2,5] => 2
[1,4,3,5,2] => 3
[1,4,5,2,3] => 3
[1,4,5,3,2] => 4
[1,5,2,3,4] => 1
[1,5,2,4,3] => 2
[1,5,3,2,4] => 2
[1,5,3,4,2] => 3
[1,5,4,2,3] => 3
[1,5,4,3,2] => 4
[2,1,3,4,5] => 1
[2,1,3,5,4] => 2
[2,1,4,3,5] => 2
[2,1,4,5,3] => 3
[2,1,5,3,4] => 2
[2,1,5,4,3] => 3
[2,3,1,4,5] => 2
[2,3,1,5,4] => 3
[2,3,4,1,5] => 3
[2,3,4,5,1] => 4
[2,3,5,1,4] => 3
[2,3,5,4,1] => 4
[2,4,1,3,5] => 2
[2,4,1,5,3] => 3
[2,4,3,1,5] => 3
[2,4,3,5,1] => 4
[2,4,5,1,3] => 4
[2,4,5,3,1] => 5
[2,5,1,3,4] => 2
[2,5,1,4,3] => 3
[2,5,3,1,4] => 3
[2,5,3,4,1] => 4
[2,5,4,1,3] => 4
[2,5,4,3,1] => 5
[3,1,2,4,5] => 1
[3,1,2,5,4] => 2
[3,1,4,2,5] => 2
[3,1,4,5,2] => 3
[3,1,5,2,4] => 2
[3,1,5,4,2] => 3
[3,2,1,4,5] => 2
[3,2,1,5,4] => 3
[3,2,4,1,5] => 3
[3,2,4,5,1] => 4
[3,2,5,1,4] => 3
[3,2,5,4,1] => 4
[3,4,1,2,5] => 3
[3,4,1,5,2] => 4
[3,4,2,1,5] => 4
[3,4,2,5,1] => 5
[3,4,5,1,2] => 5
[3,4,5,2,1] => 6
[3,5,1,2,4] => 3
[3,5,1,4,2] => 4
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Description
The number of visible inversions of a permutation.
A visible inversion of a permutation $\pi$ is a pair $i < j$ such that $\pi(j) \leq \min(i, \pi(i))$.
A visible inversion of a permutation $\pi$ is a pair $i < j$ such that $\pi(j) \leq \min(i, \pi(i))$.
References
[1] Hamaker, Z., Marberg, E., Pawlowski, B. Schur $P$-positivity and involution Stanley symmetric functions MathSciNet:4023763
Code
def statistic(pi):
return sum(1 for i in range(len(pi)) for j in range(i+1, len(pi)) if pi[j] <= min(i+1, pi[i]))
Created
Jun 14, 2021 at 12:56 by Martin Rubey
Updated
Jun 14, 2021 at 20:20 by Zachary Hamaker
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