Identifier
- St001412: 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] => 3
[3,1,2] => 3
[3,2,1] => 4
[1,2,3,4] => 0
[1,2,4,3] => 1
[1,3,2,4] => 1
[1,3,4,2] => 3
[1,4,2,3] => 3
[1,4,3,2] => 4
[2,1,3,4] => 1
[2,1,4,3] => 2
[2,3,1,4] => 3
[2,3,4,1] => 6
[2,4,1,3] => 5
[2,4,3,1] => 7
[3,1,2,4] => 3
[3,1,4,2] => 5
[3,2,1,4] => 4
[3,2,4,1] => 7
[3,4,1,2] => 6
[3,4,2,1] => 7
[4,1,2,3] => 6
[4,1,3,2] => 7
[4,2,1,3] => 7
[4,2,3,1] => 9
[4,3,1,2] => 7
[4,3,2,1] => 8
[1,2,3,4,5] => 0
[1,2,3,5,4] => 1
[1,2,4,3,5] => 1
[1,2,4,5,3] => 3
[1,2,5,3,4] => 3
[1,2,5,4,3] => 4
[1,3,2,4,5] => 1
[1,3,2,5,4] => 2
[1,3,4,2,5] => 3
[1,3,4,5,2] => 6
[1,3,5,2,4] => 5
[1,3,5,4,2] => 7
[1,4,2,3,5] => 3
[1,4,2,5,3] => 5
[1,4,3,2,5] => 4
[1,4,3,5,2] => 7
[1,4,5,2,3] => 6
[1,4,5,3,2] => 7
[1,5,2,3,4] => 6
[1,5,2,4,3] => 7
[1,5,3,2,4] => 7
[1,5,3,4,2] => 9
[1,5,4,2,3] => 7
[1,5,4,3,2] => 8
[2,1,3,4,5] => 1
[2,1,3,5,4] => 2
[2,1,4,3,5] => 2
[2,1,4,5,3] => 4
[2,1,5,3,4] => 4
[2,1,5,4,3] => 5
[2,3,1,4,5] => 3
[2,3,1,5,4] => 4
[2,3,4,1,5] => 6
[2,3,4,5,1] => 10
[2,3,5,1,4] => 8
[2,3,5,4,1] => 11
[2,4,1,3,5] => 5
[2,4,1,5,3] => 7
[2,4,3,1,5] => 7
[2,4,3,5,1] => 11
[2,4,5,1,3] => 9
[2,4,5,3,1] => 11
[2,5,1,3,4] => 8
[2,5,1,4,3] => 9
[2,5,3,1,4] => 10
[2,5,3,4,1] => 13
[2,5,4,1,3] => 10
[2,5,4,3,1] => 12
[3,1,2,4,5] => 3
[3,1,2,5,4] => 4
[3,1,4,2,5] => 5
[3,1,4,5,2] => 8
[3,1,5,2,4] => 7
[3,1,5,4,2] => 9
[3,2,1,4,5] => 4
[3,2,1,5,4] => 5
[3,2,4,1,5] => 7
[3,2,4,5,1] => 11
[3,2,5,1,4] => 9
[3,2,5,4,1] => 12
[3,4,1,2,5] => 6
[3,4,1,5,2] => 9
[3,4,2,1,5] => 7
[3,4,2,5,1] => 11
[3,4,5,1,2] => 9
[3,4,5,2,1] => 10
[3,5,1,2,4] => 9
[3,5,1,4,2] => 11
>>> Load all 1200 entries. <<<
search for individual values
searching the database for the individual values of this statistic
/
search for generating function
searching the database for statistics with the same generating function
Description
Number of minimal entries in the Bruhat order matrix of a permutation.
Associate to a permutation $\sigma$ of length $n$ the $n \times n$ matrix with entries
$$r_{ij}(\sigma) = \left| \big\{ u \in \{1,\dots,i\} \mid \sigma(u) \leq j \big\}\right|.$$
For the identity permutation, one has $r_{ij} = \min\{i,j\}$, and $\sigma \leq \tau$ in the (strong) Bruhat order if and only if $r_{ij}(\tau) \leq r_{ij}(\sigma)$ for all $i,j$.
This statistic records the number of indices $i,j$ with $r_{ij} = \min\{i,j\}$.
Associate to a permutation $\sigma$ of length $n$ the $n \times n$ matrix with entries
$$r_{ij}(\sigma) = \left| \big\{ u \in \{1,\dots,i\} \mid \sigma(u) \leq j \big\}\right|.$$
For the identity permutation, one has $r_{ij} = \min\{i,j\}$, and $\sigma \leq \tau$ in the (strong) Bruhat order if and only if $r_{ij}(\tau) \leq r_{ij}(\sigma)$ for all $i,j$.
This statistic records the number of indices $i,j$ with $r_{ij} = \min\{i,j\}$.
Code
def B(sigma):
n = len(sigma)
return Matrix([[sum(1 for u in [1 .. i] if sigma(u) <= j) for i in [1 .. n]] for j in [1 .. n]])
def statistic(sigma):
n = len(sigma)
M = B(sigma)
return sum(1 for i in range(n) for j in range(n) if M[i,j] == min(i,j))
Created
Jun 06, 2019 at 13:50 by Christian Stump
Updated
Jun 06, 2019 at 13:50 by Christian Stump
searching the database
Sorry, this statistic was not found in the database
or
add this statistic to the database – it's very simple and we need your support!