Identifier
- St000338: Permutations ⟶ ℤ
Values
[1] => 1
[1,2] => 2
[2,1] => 0
[1,2,3] => 3
[1,3,2] => 1
[2,1,3] => 0
[2,3,1] => 1
[3,1,2] => 0
[3,2,1] => 1
[1,2,3,4] => 4
[1,2,4,3] => 2
[1,3,2,4] => 1
[1,3,4,2] => 2
[1,4,2,3] => 1
[1,4,3,2] => 2
[2,1,3,4] => 0
[2,1,4,3] => 0
[2,3,1,4] => 1
[2,3,4,1] => 2
[2,4,1,3] => 1
[2,4,3,1] => 2
[3,1,2,4] => 0
[3,1,4,2] => 0
[3,2,1,4] => 1
[3,2,4,1] => 0
[3,4,1,2] => 1
[3,4,2,1] => 2
[4,1,2,3] => 0
[4,1,3,2] => 0
[4,2,1,3] => 1
[4,2,3,1] => 0
[4,3,1,2] => 1
[4,3,2,1] => 0
[1,2,3,4,5] => 5
[1,2,3,5,4] => 3
[1,2,4,3,5] => 2
[1,2,4,5,3] => 3
[1,2,5,3,4] => 2
[1,2,5,4,3] => 3
[1,3,2,4,5] => 1
[1,3,2,5,4] => 1
[1,3,4,2,5] => 2
[1,3,4,5,2] => 3
[1,3,5,2,4] => 2
[1,3,5,4,2] => 3
[1,4,2,3,5] => 1
[1,4,2,5,3] => 1
[1,4,3,2,5] => 2
[1,4,3,5,2] => 1
[1,4,5,2,3] => 2
[1,4,5,3,2] => 3
[1,5,2,3,4] => 1
[1,5,2,4,3] => 1
[1,5,3,2,4] => 2
[1,5,3,4,2] => 1
[1,5,4,2,3] => 2
[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] => 1
[2,3,1,5,4] => 1
[2,3,4,1,5] => 2
[2,3,4,5,1] => 3
[2,3,5,1,4] => 2
[2,3,5,4,1] => 3
[2,4,1,3,5] => 1
[2,4,1,5,3] => 1
[2,4,3,1,5] => 2
[2,4,3,5,1] => 1
[2,4,5,1,3] => 2
[2,4,5,3,1] => 3
[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] => 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] => 0
[3,2,4,5,1] => 0
[3,2,5,1,4] => 0
[3,2,5,4,1] => 0
[3,4,1,2,5] => 1
[3,4,1,5,2] => 1
[3,4,2,1,5] => 2
[3,4,2,5,1] => 1
[3,4,5,1,2] => 2
[3,4,5,2,1] => 3
[3,5,1,2,4] => 1
[3,5,1,4,2] => 1
>>> Load all 873 entries. <<<
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Description
The number of pixed points of a permutation.
For a permutation $\sigma = p \tau_{1} \tau_{2} \cdots \tau_{k}$ in its hook factorization, [1] defines
$$\textrm{pix} \, \sigma = \textrm{length} (p)$$.
For a permutation $\sigma = p \tau_{1} \tau_{2} \cdots \tau_{k}$ in its hook factorization, [1] defines
$$\textrm{pix} \, \sigma = \textrm{length} (p)$$.
References
[1] Foata, D., Han, G.-N. Fix-Mahonian Calculus III; a Quadruple Distribution arXiv:math/0703454
Code
def hook_factorization(w):
"""
sage: w=[1,2,4,5,6,4,5,6,4,1,3,6,5,5,4,6,1,1,4,5,1,1]
sage: hook_factorization(w)
[[1, 2, 4, 5],
[6, 4, 5, 6],
[4, 1, 3],
[6, 5],
[5, 4],
[6, 1, 1, 4],
[5, 1, 1]]
sage: w=[1,3,4,14,12,2,5,11,15,8,6,7,13,9,10]
sage: hook_factorization(w)
[[1, 3, 4, 14], [12, 2, 5, 11, 15], [8, 6, 7], [13, 9, 10]]
"""
if len(w) == 0:
return []
w1 = w + [max(w)+1]
i = len(w)-1
while w1[i] <= w1[i+1]:
i -= 1
if i == -1:
return [w]
else:
return hook_factorization(w[:i]) + [w[i:]]
def statistic(pi):
p0 = hook_factorization(pi)[0]
if len(p0) == 1 or p0[0] < p0[1]:
return len(p0)
else:
return 0
Created
Dec 18, 2015 at 13:44 by Joseph Bernstein
Updated
Apr 06, 2016 at 22:50 by Martin Rubey
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