Identifier
- St001160: Permutations ⟶ ℤ
Values
[1] => 0
[1,2] => 0
[2,1] => 0
[1,2,3] => 2
[1,3,2] => 1
[2,1,3] => 1
[2,3,1] => 1
[3,1,2] => 1
[3,2,1] => 2
[1,2,3,4] => 5
[1,2,4,3] => 3
[1,3,2,4] => 3
[1,3,4,2] => 2
[1,4,2,3] => 2
[1,4,3,2] => 3
[2,1,3,4] => 3
[2,1,4,3] => 2
[2,3,1,4] => 2
[2,3,4,1] => 3
[2,4,1,3] => 0
[2,4,3,1] => 2
[3,1,2,4] => 2
[3,1,4,2] => 0
[3,2,1,4] => 3
[3,2,4,1] => 2
[3,4,1,2] => 2
[3,4,2,1] => 3
[4,1,2,3] => 3
[4,1,3,2] => 2
[4,2,1,3] => 2
[4,2,3,1] => 3
[4,3,1,2] => 3
[4,3,2,1] => 5
[1,2,3,4,5] => 9
[1,2,3,5,4] => 6
[1,2,4,3,5] => 6
[1,2,4,5,3] => 4
[1,2,5,3,4] => 4
[1,2,5,4,3] => 5
[1,3,2,4,5] => 6
[1,3,2,5,4] => 4
[1,3,4,2,5] => 4
[1,3,4,5,2] => 4
[1,3,5,2,4] => 1
[1,3,5,4,2] => 3
[1,4,2,3,5] => 4
[1,4,2,5,3] => 1
[1,4,3,2,5] => 5
[1,4,3,5,2] => 3
[1,4,5,2,3] => 3
[1,4,5,3,2] => 4
[1,5,2,3,4] => 4
[1,5,2,4,3] => 3
[1,5,3,2,4] => 3
[1,5,3,4,2] => 4
[1,5,4,2,3] => 4
[1,5,4,3,2] => 6
[2,1,3,4,5] => 6
[2,1,3,5,4] => 4
[2,1,4,3,5] => 4
[2,1,4,5,3] => 3
[2,1,5,3,4] => 3
[2,1,5,4,3] => 4
[2,3,1,4,5] => 4
[2,3,1,5,4] => 3
[2,3,4,1,5] => 4
[2,3,4,5,1] => 6
[2,3,5,1,4] => 1
[2,3,5,4,1] => 4
[2,4,1,3,5] => 1
[2,4,1,5,3] => 0
[2,4,3,1,5] => 3
[2,4,3,5,1] => 4
[2,4,5,1,3] => 1
[2,4,5,3,1] => 3
[2,5,1,3,4] => 1
[2,5,1,4,3] => 1
[2,5,3,1,4] => 0
[2,5,3,4,1] => 3
[2,5,4,1,3] => 1
[2,5,4,3,1] => 4
[3,1,2,4,5] => 4
[3,1,2,5,4] => 3
[3,1,4,2,5] => 1
[3,1,4,5,2] => 1
[3,1,5,2,4] => 0
[3,1,5,4,2] => 1
[3,2,1,4,5] => 5
[3,2,1,5,4] => 4
[3,2,4,1,5] => 3
[3,2,4,5,1] => 4
[3,2,5,1,4] => 1
[3,2,5,4,1] => 3
[3,4,1,2,5] => 3
[3,4,1,5,2] => 1
[3,4,2,1,5] => 4
[3,4,2,5,1] => 3
[3,4,5,1,2] => 4
[3,4,5,2,1] => 5
[3,5,1,2,4] => 1
[3,5,1,4,2] => 0
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Description
The number of proper blocks (or intervals) of a permutations.
Let $\pi = [\pi_1,\ldots,\pi_n]$ be a permutation. A block (or interval) of $\pi$ is then a consecutive subpattern $\pi_i,\ldots,\pi_{i+k}$ whose values form a set of contiguous integers.
Let $\pi = [\pi_1,\ldots,\pi_n]$ be a permutation. A block (or interval) of $\pi$ is then a consecutive subpattern $\pi_i,\ldots,\pi_{i+k}$ whose values form a set of contiguous integers.
References
[1] Adin, R. M., Bagno, E., Eisenberg, E., Reches, S., Sigron, M. Towards a Combinatorial proof of Gessel's conjecture on two-sided Gamma positivity: A reduction to simple permutations arXiv:1711.06511
Code
def statistic(pi):
pi = list(pi)
n = len(pi)
if n <= 2:
return 0
else:
return sum(1 for j in range(n) for i in range(j) if max(pi[i:j+1])-min(pi[i:j+1]) == j-i) - 1
Created
Apr 24, 2018 at 10:28 by Christian Stump
Updated
Apr 24, 2018 at 10:53 by Christian Stump
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