Identifier
Identifier
Values
[1,2] => 0
[2,1] => 0
[1,2,3] => 0
[1,3,2] => 0
[2,1,3] => 0
[2,3,1] => 0
[3,1,2] => 0
[3,2,1] => 0
[1,2,3,4] => 0
[1,2,4,3] => 0
[1,3,2,4] => 0
[1,3,4,2] => 0
[1,4,2,3] => 0
[1,4,3,2] => 0
[2,1,3,4] => 0
[2,1,4,3] => 0
[2,3,1,4] => 0
[2,3,4,1] => 1
[2,4,1,3] => 0
[2,4,3,1] => 1
[3,1,2,4] => 0
[3,1,4,2] => 1
[3,2,1,4] => 0
[3,2,4,1] => 1
[3,4,1,2] => 1
[3,4,2,1] => 1
[4,1,2,3] => 1
[4,1,3,2] => 1
[4,2,1,3] => 1
[4,2,3,1] => 1
[4,3,1,2] => 1
[4,3,2,1] => 1
[1,2,3,4,5] => 0
[1,2,3,5,4] => 0
[1,2,4,3,5] => 0
[1,2,4,5,3] => 0
[1,2,5,3,4] => 0
[1,2,5,4,3] => 0
[1,3,2,4,5] => 0
[1,3,2,5,4] => 0
[1,3,4,2,5] => 0
[1,3,4,5,2] => 1
[1,3,5,2,4] => 0
[1,3,5,4,2] => 1
[1,4,2,3,5] => 0
[1,4,2,5,3] => 1
[1,4,3,2,5] => 0
[1,4,3,5,2] => 1
[1,4,5,2,3] => 1
[1,4,5,3,2] => 1
[1,5,2,3,4] => 1
[1,5,2,4,3] => 1
[1,5,3,2,4] => 1
[1,5,3,4,2] => 1
[1,5,4,2,3] => 1
[1,5,4,3,2] => 1
[2,1,3,4,5] => 0
[2,1,3,5,4] => 0
[2,1,4,3,5] => 0
[2,1,4,5,3] => 0
[2,1,5,3,4] => 0
[2,1,5,4,3] => 0
[2,3,1,4,5] => 0
[2,3,1,5,4] => 0
[2,3,4,1,5] => 1
[2,3,4,5,1] => 1
[2,3,5,1,4] => 1
[2,3,5,4,1] => 1
[2,4,1,3,5] => 0
[2,4,1,5,3] => 1
[2,4,3,1,5] => 1
[2,4,3,5,1] => 1
[2,4,5,1,3] => 2
[2,4,5,3,1] => 1
[2,5,1,3,4] => 1
[2,5,1,4,3] => 1
[2,5,3,1,4] => 2
[2,5,3,4,1] => 1
[2,5,4,1,3] => 2
[2,5,4,3,1] => 1
[3,1,2,4,5] => 0
[3,1,2,5,4] => 0
[3,1,4,2,5] => 1
[3,1,4,5,2] => 0
[3,1,5,2,4] => 1
[3,1,5,4,2] => 0
[3,2,1,4,5] => 0
[3,2,1,5,4] => 0
[3,2,4,1,5] => 1
[3,2,4,5,1] => 1
[3,2,5,1,4] => 1
[3,2,5,4,1] => 1
[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] => 2
[3,4,5,2,1] => 2
[3,5,1,2,4] => 2
[3,5,1,4,2] => 1
[3,5,2,1,4] => 2
[3,5,2,4,1] => 1
[3,5,4,1,2] => 2
[3,5,4,2,1] => 2
[4,1,2,3,5] => 1
[4,1,2,5,3] => 0
[4,1,3,2,5] => 1
[4,1,3,5,2] => 0
[4,1,5,2,3] => 1
[4,1,5,3,2] => 1
[4,2,1,3,5] => 1
[4,2,1,5,3] => 0
[4,2,3,1,5] => 1
[4,2,3,5,1] => 1
[4,2,5,1,3] => 1
[4,2,5,3,1] => 2
[4,3,1,2,5] => 1
[4,3,1,5,2] => 1
[4,3,2,1,5] => 1
[4,3,2,5,1] => 1
[4,3,5,1,2] => 2
[4,3,5,2,1] => 2
[4,5,1,2,3] => 2
[4,5,1,3,2] => 2
[4,5,2,1,3] => 2
[4,5,2,3,1] => 2
[4,5,3,1,2] => 2
[4,5,3,2,1] => 2
[5,1,2,3,4] => 1
[5,1,2,4,3] => 1
[5,1,3,2,4] => 1
[5,1,3,4,2] => 1
[5,1,4,2,3] => 1
[5,1,4,3,2] => 1
[5,2,1,3,4] => 1
[5,2,1,4,3] => 1
[5,2,3,1,4] => 1
[5,2,3,4,1] => 2
[5,2,4,1,3] => 1
[5,2,4,3,1] => 2
[5,3,1,2,4] => 1
[5,3,1,4,2] => 2
[5,3,2,1,4] => 1
[5,3,2,4,1] => 2
[5,3,4,1,2] => 2
[5,3,4,2,1] => 2
[5,4,1,2,3] => 2
[5,4,1,3,2] => 2
[5,4,2,1,3] => 2
[5,4,2,3,1] => 2
[5,4,3,1,2] => 2
[5,4,3,2,1] => 2
click to show generating function       
Description
The number of strict-3-descents.
A strict-3-descent of a permutation $\pi$ of $\{1,2, \dots ,n \}$ is a pair $(i,i+3)$ with $ i+3 \leq n$ and $\pi(i) > \pi(i+3)$.
Code
def statistic(pi):
	return sum(1 for i in range(len(pi)-3) if pi[i]>pi[i+3])

Created
Feb 20, 2020 at 16:09 by Kathrin Meier
Updated
Feb 20, 2020 at 16:09 by Kathrin Meier