Identifier
- St000365: Permutations ⟶ ℤ
Values
[1] => 0
[1,2] => 0
[2,1] => 0
[1,2,3] => 1
[1,3,2] => 0
[2,1,3] => 0
[2,3,1] => 0
[3,1,2] => 0
[3,2,1] => 0
[1,2,3,4] => 2
[1,2,4,3] => 1
[1,3,2,4] => 0
[1,3,4,2] => 1
[1,4,2,3] => 0
[1,4,3,2] => 0
[2,1,3,4] => 1
[2,1,4,3] => 0
[2,3,1,4] => 0
[2,3,4,1] => 1
[2,4,1,3] => 0
[2,4,3,1] => 0
[3,1,2,4] => 1
[3,1,4,2] => 0
[3,2,1,4] => 0
[3,2,4,1] => 0
[3,4,1,2] => 0
[3,4,2,1] => 0
[4,1,2,3] => 1
[4,1,3,2] => 0
[4,2,1,3] => 0
[4,2,3,1] => 0
[4,3,1,2] => 0
[4,3,2,1] => 0
[1,2,3,4,5] => 3
[1,2,3,5,4] => 2
[1,2,4,3,5] => 1
[1,2,4,5,3] => 2
[1,2,5,3,4] => 1
[1,2,5,4,3] => 1
[1,3,2,4,5] => 1
[1,3,2,5,4] => 0
[1,3,4,2,5] => 1
[1,3,4,5,2] => 2
[1,3,5,2,4] => 1
[1,3,5,4,2] => 1
[1,4,2,3,5] => 1
[1,4,2,5,3] => 0
[1,4,3,2,5] => 0
[1,4,3,5,2] => 0
[1,4,5,2,3] => 1
[1,4,5,3,2] => 1
[1,5,2,3,4] => 1
[1,5,2,4,3] => 0
[1,5,3,2,4] => 0
[1,5,3,4,2] => 0
[1,5,4,2,3] => 0
[1,5,4,3,2] => 0
[2,1,3,4,5] => 2
[2,1,3,5,4] => 1
[2,1,4,3,5] => 0
[2,1,4,5,3] => 1
[2,1,5,3,4] => 0
[2,1,5,4,3] => 0
[2,3,1,4,5] => 1
[2,3,1,5,4] => 0
[2,3,4,1,5] => 1
[2,3,4,5,1] => 2
[2,3,5,1,4] => 1
[2,3,5,4,1] => 1
[2,4,1,3,5] => 1
[2,4,1,5,3] => 0
[2,4,3,1,5] => 0
[2,4,3,5,1] => 0
[2,4,5,1,3] => 1
[2,4,5,3,1] => 1
[2,5,1,3,4] => 1
[2,5,1,4,3] => 0
[2,5,3,1,4] => 0
[2,5,3,4,1] => 0
[2,5,4,1,3] => 0
[2,5,4,3,1] => 0
[3,1,2,4,5] => 2
[3,1,2,5,4] => 1
[3,1,4,2,5] => 0
[3,1,4,5,2] => 1
[3,1,5,2,4] => 0
[3,1,5,4,2] => 0
[3,2,1,4,5] => 1
[3,2,1,5,4] => 0
[3,2,4,1,5] => 0
[3,2,4,5,1] => 1
[3,2,5,1,4] => 0
[3,2,5,4,1] => 0
[3,4,1,2,5] => 1
[3,4,1,5,2] => 0
[3,4,2,1,5] => 0
[3,4,2,5,1] => 0
[3,4,5,1,2] => 1
[3,4,5,2,1] => 1
[3,5,1,2,4] => 1
[3,5,1,4,2] => 0
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Description
The number of double ascents of a permutation.
A double ascent of a permutation $\pi$ is a position $i$ such that $\pi(i) < \pi(i+1) < \pi(i+2)$.
A double ascent of a permutation $\pi$ is a position $i$ such that $\pi(i) < \pi(i+1) < \pi(i+2)$.
References
[1] Ma, S.-M., Yeh, Y.-N. The peak statistics on simsun permutations arXiv:1601.06505
Code
def statistic(pi):
return sum( 1 for i in range(len(pi)-2) if pi[i]
Created
Jan 26, 2016 at 20:56 by Christian Stump
Updated
May 10, 2019 at 17:27 by Henning Ulfarsson
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