Identifier
- St000111: Permutations ⟶ ℤ
Values
[1] => 0
[1,2] => 0
[2,1] => 2
[1,2,3] => 0
[1,3,2] => 3
[2,1,3] => 2
[2,3,1] => 3
[3,1,2] => 3
[3,2,1] => 5
[1,2,3,4] => 0
[1,2,4,3] => 4
[1,3,2,4] => 3
[1,3,4,2] => 4
[1,4,2,3] => 4
[1,4,3,2] => 7
[2,1,3,4] => 2
[2,1,4,3] => 6
[2,3,1,4] => 3
[2,3,4,1] => 4
[2,4,1,3] => 4
[2,4,3,1] => 7
[3,1,2,4] => 3
[3,1,4,2] => 7
[3,2,1,4] => 5
[3,2,4,1] => 7
[3,4,1,2] => 4
[3,4,2,1] => 6
[4,1,2,3] => 4
[4,1,3,2] => 7
[4,2,1,3] => 6
[4,2,3,1] => 7
[4,3,1,2] => 7
[4,3,2,1] => 9
[1,2,3,4,5] => 0
[1,2,3,5,4] => 5
[1,2,4,3,5] => 4
[1,2,4,5,3] => 5
[1,2,5,3,4] => 5
[1,2,5,4,3] => 9
[1,3,2,4,5] => 3
[1,3,2,5,4] => 8
[1,3,4,2,5] => 4
[1,3,4,5,2] => 5
[1,3,5,2,4] => 5
[1,3,5,4,2] => 9
[1,4,2,3,5] => 4
[1,4,2,5,3] => 9
[1,4,3,2,5] => 7
[1,4,3,5,2] => 9
[1,4,5,2,3] => 5
[1,4,5,3,2] => 8
[1,5,2,3,4] => 5
[1,5,2,4,3] => 9
[1,5,3,2,4] => 8
[1,5,3,4,2] => 9
[1,5,4,2,3] => 9
[1,5,4,3,2] => 12
[2,1,3,4,5] => 2
[2,1,3,5,4] => 7
[2,1,4,3,5] => 6
[2,1,4,5,3] => 7
[2,1,5,3,4] => 7
[2,1,5,4,3] => 11
[2,3,1,4,5] => 3
[2,3,1,5,4] => 8
[2,3,4,1,5] => 4
[2,3,4,5,1] => 5
[2,3,5,1,4] => 5
[2,3,5,4,1] => 9
[2,4,1,3,5] => 4
[2,4,1,5,3] => 9
[2,4,3,1,5] => 7
[2,4,3,5,1] => 9
[2,4,5,1,3] => 5
[2,4,5,3,1] => 8
[2,5,1,3,4] => 5
[2,5,1,4,3] => 9
[2,5,3,1,4] => 8
[2,5,3,4,1] => 9
[2,5,4,1,3] => 9
[2,5,4,3,1] => 12
[3,1,2,4,5] => 3
[3,1,2,5,4] => 8
[3,1,4,2,5] => 7
[3,1,4,5,2] => 8
[3,1,5,2,4] => 8
[3,1,5,4,2] => 12
[3,2,1,4,5] => 5
[3,2,1,5,4] => 10
[3,2,4,1,5] => 7
[3,2,4,5,1] => 8
[3,2,5,1,4] => 8
[3,2,5,4,1] => 12
[3,4,1,2,5] => 4
[3,4,1,5,2] => 9
[3,4,2,1,5] => 6
[3,4,2,5,1] => 9
[3,4,5,1,2] => 5
[3,4,5,2,1] => 7
[3,5,1,2,4] => 5
[3,5,1,4,2] => 9
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Description
The sum of the descent tops (or Genocchi descents) of a permutation.
This statistic is given by
$$\pi \mapsto \sum_{i\in\operatorname{Des}(\pi)} \pi_i.$$
This statistic is given by
$$\pi \mapsto \sum_{i\in\operatorname{Des}(\pi)} \pi_i.$$
References
[1] Babson, E., Steingr'ımsson, E. Generalized permutation patterns and a classification of the Mahonian statistics MathSciNet:1758852
[2] Nunge, A. An equivalence of multistatistics on permutations arXiv:1601.02928
[3] Clarke, R. J., Steingr'ımsson, E., Zeng, J. New Euler-Mahonian statistics on permutations and words MathSciNet:1436481
[2] Nunge, A. An equivalence of multistatistics on permutations arXiv:1601.02928
[3] Clarke, R. J., Steingr'ımsson, E., Zeng, J. New Euler-Mahonian statistics on permutations and words MathSciNet:1436481
Code
def statistic(pi):
return sum( pi[i] for i in range(pi.size()-1) if pi[i] > pi[i+1] )
Created
Jun 15, 2013 at 13:31 by Chris Berg
Updated
Apr 06, 2016 at 06:56 by Martin Rubey
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