Identifier
- St000530: Permutations ⟶ ℤ
Values
[1,2] => 1
[2,1] => 1
[1,2,3] => 1
[1,3,2] => 2
[2,1,3] => 2
[2,3,1] => 2
[3,1,2] => 2
[3,2,1] => 1
[1,2,3,4] => 1
[1,2,4,3] => 3
[1,3,2,4] => 5
[1,3,4,2] => 3
[1,4,2,3] => 5
[1,4,3,2] => 3
[2,1,3,4] => 3
[2,1,4,3] => 5
[2,3,1,4] => 5
[2,3,4,1] => 3
[2,4,1,3] => 5
[2,4,3,1] => 3
[3,1,2,4] => 3
[3,1,4,2] => 5
[3,2,1,4] => 3
[3,2,4,1] => 5
[3,4,1,2] => 5
[3,4,2,1] => 3
[4,1,2,3] => 3
[4,1,3,2] => 5
[4,2,1,3] => 3
[4,2,3,1] => 5
[4,3,1,2] => 3
[4,3,2,1] => 1
[1,2,3,4,5] => 1
[1,2,3,5,4] => 4
[1,2,4,3,5] => 9
[1,2,4,5,3] => 4
[1,2,5,3,4] => 9
[1,2,5,4,3] => 6
[1,3,2,4,5] => 9
[1,3,2,5,4] => 16
[1,3,4,2,5] => 9
[1,3,4,5,2] => 4
[1,3,5,2,4] => 9
[1,3,5,4,2] => 6
[1,4,2,3,5] => 9
[1,4,2,5,3] => 16
[1,4,3,2,5] => 11
[1,4,3,5,2] => 16
[1,4,5,2,3] => 9
[1,4,5,3,2] => 6
[1,5,2,3,4] => 9
[1,5,2,4,3] => 16
[1,5,3,2,4] => 11
[1,5,3,4,2] => 16
[1,5,4,2,3] => 11
[1,5,4,3,2] => 4
[2,1,3,4,5] => 4
[2,1,3,5,4] => 11
[2,1,4,3,5] => 16
[2,1,4,5,3] => 11
[2,1,5,3,4] => 16
[2,1,5,4,3] => 9
[2,3,1,4,5] => 9
[2,3,1,5,4] => 16
[2,3,4,1,5] => 9
[2,3,4,5,1] => 4
[2,3,5,1,4] => 9
[2,3,5,4,1] => 6
[2,4,1,3,5] => 9
[2,4,1,5,3] => 16
[2,4,3,1,5] => 11
[2,4,3,5,1] => 16
[2,4,5,1,3] => 9
[2,4,5,3,1] => 6
[2,5,1,3,4] => 9
[2,5,1,4,3] => 16
[2,5,3,1,4] => 11
[2,5,3,4,1] => 16
[2,5,4,1,3] => 11
[2,5,4,3,1] => 4
[3,1,2,4,5] => 4
[3,1,2,5,4] => 11
[3,1,4,2,5] => 16
[3,1,4,5,2] => 11
[3,1,5,2,4] => 16
[3,1,5,4,2] => 9
[3,2,1,4,5] => 6
[3,2,1,5,4] => 9
[3,2,4,1,5] => 16
[3,2,4,5,1] => 11
[3,2,5,1,4] => 16
[3,2,5,4,1] => 9
[3,4,1,2,5] => 9
[3,4,1,5,2] => 16
[3,4,2,1,5] => 11
[3,4,2,5,1] => 16
[3,4,5,1,2] => 9
[3,4,5,2,1] => 6
[3,5,1,2,4] => 9
[3,5,1,4,2] => 16
[3,5,2,1,4] => 11
>>> Load all 1200 entries. <<<
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Description
The number of permutations with the same descent word as the given permutation.
The descent word of a permutation is the binary word given by Mp00109descent word. For a given permutation, this statistic is the number of permutations with the same descent word, so the number of elements in the fiber of the map Mp00109descent word containing a given permutation.
This statistic appears as up-down analysis in statistical applications in genetics, see [1] and the references therein.
The descent word of a permutation is the binary word given by Mp00109descent word. For a given permutation, this statistic is the number of permutations with the same descent word, so the number of elements in the fiber of the map Mp00109descent word containing a given permutation.
This statistic appears as up-down analysis in statistical applications in genetics, see [1] and the references therein.
References
[1] Morton, J., Pachter, L., Shiu, A., Sturmfels, B., Wienand, O. Convex rank tests and semigraphoids MathSciNet:2538642
Code
from collections import defaultdict
def word(pi):
w = [0]*(len(pi)-1)
for i in pi.descents(from_zero=True):
w[i] = 1
return Words([0,1])(w)
@cached_function
def preimages(n):
D = defaultdict(int)
for pi in Permutations(n):
D[word(pi)] += 1
return D
def statistic(pi):
return preimages(len(pi))[word(pi)]
Created
Jun 10, 2016 at 08:54 by Christian Stump
Updated
Jan 15, 2018 at 08:00 by Martin Rubey
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