Identifier
- St000653: Permutations ⟶ ℤ
Values
[1,2] => 0
[2,1] => 1
[1,2,3] => 0
[1,3,2] => 2
[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] => 3
[1,3,2,4] => 2
[1,3,4,2] => 3
[1,4,2,3] => 2
[1,4,3,2] => 3
[2,1,3,4] => 1
[2,1,4,3] => 3
[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] => 3
[3,2,1,4] => 2
[3,2,4,1] => 3
[3,4,1,2] => 2
[3,4,2,1] => 3
[4,1,2,3] => 1
[4,1,3,2] => 3
[4,2,1,3] => 2
[4,2,3,1] => 3
[4,3,1,2] => 2
[4,3,2,1] => 3
[1,2,3,4,5] => 0
[1,2,3,5,4] => 4
[1,2,4,3,5] => 3
[1,2,4,5,3] => 4
[1,2,5,3,4] => 3
[1,2,5,4,3] => 4
[1,3,2,4,5] => 2
[1,3,2,5,4] => 4
[1,3,4,2,5] => 3
[1,3,4,5,2] => 4
[1,3,5,2,4] => 3
[1,3,5,4,2] => 4
[1,4,2,3,5] => 2
[1,4,2,5,3] => 4
[1,4,3,2,5] => 3
[1,4,3,5,2] => 4
[1,4,5,2,3] => 3
[1,4,5,3,2] => 4
[1,5,2,3,4] => 2
[1,5,2,4,3] => 4
[1,5,3,2,4] => 3
[1,5,3,4,2] => 4
[1,5,4,2,3] => 3
[1,5,4,3,2] => 4
[2,1,3,4,5] => 1
[2,1,3,5,4] => 4
[2,1,4,3,5] => 3
[2,1,4,5,3] => 4
[2,1,5,3,4] => 3
[2,1,5,4,3] => 4
[2,3,1,4,5] => 2
[2,3,1,5,4] => 4
[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] => 4
[2,4,3,1,5] => 3
[2,4,3,5,1] => 4
[2,4,5,1,3] => 3
[2,4,5,3,1] => 4
[2,5,1,3,4] => 2
[2,5,1,4,3] => 4
[2,5,3,1,4] => 3
[2,5,3,4,1] => 4
[2,5,4,1,3] => 3
[2,5,4,3,1] => 4
[3,1,2,4,5] => 1
[3,1,2,5,4] => 4
[3,1,4,2,5] => 3
[3,1,4,5,2] => 4
[3,1,5,2,4] => 3
[3,1,5,4,2] => 4
[3,2,1,4,5] => 2
[3,2,1,5,4] => 4
[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] => 2
[3,4,1,5,2] => 4
[3,4,2,1,5] => 3
[3,4,2,5,1] => 4
[3,4,5,1,2] => 3
[3,4,5,2,1] => 4
[3,5,1,2,4] => 2
[3,5,1,4,2] => 4
[3,5,2,1,4] => 3
>>> Load all 1200 entries. <<<
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Description
The last descent of a permutation.
For a permutation $\pi$ of $\{1,\ldots,n\}$, this is the largest index $0 \leq i < n$ such that $\pi(i) > \pi(i+1)$ where one considers $\pi(0) = n+1$.
For a permutation $\pi$ of $\{1,\ldots,n\}$, this is the largest index $0 \leq i < n$ such that $\pi(i) > \pi(i+1)$ where one considers $\pi(0) = n+1$.
References
[1] Adin, R. M., Bagno, E., Roichman, Y. Block decomposition of permutations and Schur-positivity arXiv:1611.06979
Code
def statistic(pi):
Des = [0] + pi.descents(from_zero=False)
return Des[-1]
Created
Nov 22, 2016 at 14:26 by Christian Stump
Updated
Nov 25, 2016 at 18:39 by Martin Rubey
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