- FindStat

Identifier

St001557: Permutations ⟶ ℤ

Values

=>
                            
                            
                            
                            

                        [1,2]=>0
[2,1]=>0
[1,2,3]=>0
[1,3,2]=>1
[2,1,3]=>0
[2,3,1]=>1
[3,1,2]=>0
[3,2,1]=>1
[1,2,3,4]=>0
[1,2,4,3]=>0
[1,3,2,4]=>1
[1,3,4,2]=>1
[1,4,2,3]=>2
[1,4,3,2]=>2
[2,1,3,4]=>0
[2,1,4,3]=>0
[2,3,1,4]=>1
[2,3,4,1]=>1
[2,4,1,3]=>2
[2,4,3,1]=>2
[3,1,2,4]=>0
[3,1,4,2]=>0
[3,2,1,4]=>1
[3,2,4,1]=>1
[3,4,1,2]=>2
[3,4,2,1]=>2
[4,1,2,3]=>0
[4,1,3,2]=>0
[4,2,1,3]=>1
[4,2,3,1]=>1
[4,3,1,2]=>2
[4,3,2,1]=>2
[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]=>1
[1,3,2,5,4]=>1
[1,3,4,2,5]=>1
[1,3,4,5,2]=>1
[1,3,5,2,4]=>1
[1,3,5,4,2]=>1
[1,4,2,3,5]=>2
[1,4,2,5,3]=>2
[1,4,3,2,5]=>2
[1,4,3,5,2]=>2
[1,4,5,2,3]=>2
[1,4,5,3,2]=>2
[1,5,2,3,4]=>3
[1,5,2,4,3]=>3
[1,5,3,2,4]=>3
[1,5,3,4,2]=>3
[1,5,4,2,3]=>3
[1,5,4,3,2]=>3
[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]=>1
[2,3,1,5,4]=>1
[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]=>2
[2,4,1,5,3]=>2
[2,4,3,1,5]=>2
[2,4,3,5,1]=>2
[2,4,5,1,3]=>2
[2,4,5,3,1]=>2
[2,5,1,3,4]=>3
[2,5,1,4,3]=>3
[2,5,3,1,4]=>3
[2,5,3,4,1]=>3
[2,5,4,1,3]=>3
[2,5,4,3,1]=>3
[3,1,2,4,5]=>0
[3,1,2,5,4]=>0
[3,1,4,2,5]=>0
[3,1,4,5,2]=>0
[3,1,5,2,4]=>0
[3,1,5,4,2]=>0
[3,2,1,4,5]=>1
[3,2,1,5,4]=>1
[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]=>2
[3,4,1,5,2]=>2
[3,4,2,1,5]=>2
[3,4,2,5,1]=>2
[3,4,5,1,2]=>2
[3,4,5,2,1]=>2
[3,5,1,2,4]=>3
[3,5,1,4,2]=>3
[3,5,2,1,4]=>3
[3,5,2,4,1]=>3
[3,5,4,1,2]=>3
[3,5,4,2,1]=>3
[4,1,2,3,5]=>0
[4,1,2,5,3]=>0
[4,1,3,2,5]=>0
[4,1,3,5,2]=>0
[4,1,5,2,3]=>0
[4,1,5,3,2]=>0
[4,2,1,3,5]=>1
[4,2,1,5,3]=>1
[4,2,3,1,5]=>1
[4,2,3,5,1]=>1
[4,2,5,1,3]=>1
[4,2,5,3,1]=>1
[4,3,1,2,5]=>2
[4,3,1,5,2]=>2
[4,3,2,1,5]=>2
[4,3,2,5,1]=>2
[4,3,5,1,2]=>2
[4,3,5,2,1]=>2
[4,5,1,2,3]=>3
[4,5,1,3,2]=>3
[4,5,2,1,3]=>3
[4,5,2,3,1]=>3
[4,5,3,1,2]=>3
[4,5,3,2,1]=>3
[5,1,2,3,4]=>0
[5,1,2,4,3]=>0
[5,1,3,2,4]=>0
[5,1,3,4,2]=>0
[5,1,4,2,3]=>0
[5,1,4,3,2]=>0
[5,2,1,3,4]=>1
[5,2,1,4,3]=>1
[5,2,3,1,4]=>1
[5,2,3,4,1]=>1
[5,2,4,1,3]=>1
[5,2,4,3,1]=>1
[5,3,1,2,4]=>2
[5,3,1,4,2]=>2
[5,3,2,1,4]=>2
[5,3,2,4,1]=>2
[5,3,4,1,2]=>2
[5,3,4,2,1]=>2
[5,4,1,2,3]=>3
[5,4,1,3,2]=>3
[5,4,2,1,3]=>3
[5,4,2,3,1]=>3
[5,4,3,1,2]=>3
[5,4,3,2,1]=>3
                    

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

click to show known generating functions

Description

The number of inversions of the second entry of a permutation.
This is, for a permutation $\pi$ of length $n$,
$$\# \{2 < k \leq n \mid \pi(2) > \pi(k)\}.$$
The number of inversions of the first entry is St000054The first entry of the permutation. and the number of inversions of the third entry is St001556The number of inversions of the third entry of a permutation.. The sequence of inversions of all the entries define the Lehmer code of a permutation.

Code

def statistic(pi):
    k=2
    n=len(pi)
    return(sum(1 for i in [k+1 .. n] if pi(k)>pi(i)))

Created

Jun 25, 2020 at 09:59 by Kathrin Meier

Updated

Jun 25, 2020 at 10:52 by Christian Stump