- FindStat

Identifier

St001520: Permutations ⟶ ℤ

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
                    

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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 09, 2021 at 17:46 by Martin Rubey