Identifier
Values
[1] => 1
[2] => 1
[1,1] => 1
[3] => 2
[2,1] => 4
[1,1,1] => 8
[4] => 5
[3,1] => 15
[2,2] => 18
[2,1,1] => 48
[1,1,1,1] => 144
[5] => 14
[4,1] => 56
[3,2] => 72
[3,1,1] => 240
[2,2,1] => 288
[2,1,1,1] => 1056
[1,1,1,1,1] => 4224
[6] => 42
[5,1] => 210
[4,2] => 280
[4,1,1] => 1120
[3,3] => 300
[3,2,1] => 1440
[3,1,1,1] => 6240
[2,2,2] => 1728
[2,2,1,1] => 7488
[2,1,1,1,1] => 34944
[1,1,1,1,1,1] => 174720
[7] => 132
[6,1] => 792
[5,2] => 1080
[5,1,1] => 5040
[4,3] => 1200
[4,2,1] => 6720
[4,1,1,1] => 33600
[3,3,1] => 7200
[3,2,2] => 8640
[3,2,1,1] => 43200
[3,1,1,1,1] => 230400
[2,2,2,1] => 51840
[2,2,1,1,1] => 276480
[2,1,1,1,1,1] => 1566720
[1,1,1,1,1,1,1] => 9400320
[8] => 429
[7,1] => 3003
[6,2] => 4158
[6,1,1] => 22176
[5,3] => 4725
[5,2,1] => 30240
[5,1,1,1] => 171360
[4,4] => 4900
[4,3,1] => 33600
[4,2,2] => 40320
[4,2,1,1] => 228480
[4,1,1,1,1] => 1370880
[3,3,2] => 43200
[3,3,1,1] => 244800
[3,2,2,1] => 293760
[3,2,1,1,1] => 1762560
[3,1,1,1,1,1] => 11162880
[2,2,2,2] => 352512
[2,2,2,1,1] => 2115072
[2,2,1,1,1,1] => 13395456
[2,1,1,1,1,1,1] => 89303040
[1,1,1,1,1,1,1,1] => 625121280
[9] => 1430
[8,1] => 11440
[7,2] => 16016
[7,1,1] => 96096
[6,3] => 18480
[6,2,1] => 133056
[6,1,1,1] => 842688
[5,4] => 19600
[5,3,1] => 151200
[5,2,2] => 181440
[5,2,1,1] => 1149120
[5,1,1,1,1] => 7660800
[4,4,1] => 156800
[4,3,2] => 201600
[4,3,1,1] => 1276800
[4,2,2,1] => 1532160
[4,2,1,1,1] => 10214400
[4,1,1,1,1,1] => 71500800
[3,3,3] => 216000
[3,3,2,1] => 1641600
[3,3,1,1,1] => 10944000
[3,2,2,2] => 1969920
[3,2,2,1,1] => 13132800
[3,2,1,1,1,1] => 91929600
[3,1,1,1,1,1,1] => 674150400
[2,2,2,2,1] => 15759360
[2,2,2,1,1,1] => 110315520
[2,2,1,1,1,1,1] => 808980480
[10] => 4862
[9,1] => 43758
[8,2] => 61776
[8,1,1] => 411840
[7,3] => 72072
[7,2,1] => 576576
[7,1,1,1] => 4036032
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Description
The number of transitive monotone factorizations of genus zero of a permutation of given cycle type.
Let $\pi$ be a permutation of cycle type $\mu$. A transitive monotone factorisation of genus zero of a permutation $\pi\in\mathfrak S_n$ is a tuple of $r = n + \ell(\mu) - 2$ transpositions
$$ (a_1, b_1),\dots,(a_r, b_r) $$
with $b_1 \leq \dots \leq b_r$ and $a_i < b_i$ for all $i$, such that the subgroup of $\mathfrak S_n$ generated by the transpositions acts transitively on $\{1,\dots,n\}$ and hose product, in this order, is $\pi$.
Let $\pi$ be a permutation of cycle type $\mu$. A transitive monotone factorisation of genus zero of a permutation $\pi\in\mathfrak S_n$ is a tuple of $r = n + \ell(\mu) - 2$ transpositions
$$ (a_1, b_1),\dots,(a_r, b_r) $$
with $b_1 \leq \dots \leq b_r$ and $a_i < b_i$ for all $i$, such that the subgroup of $\mathfrak S_n$ generated by the transpositions acts transitively on $\{1,\dots,n\}$ and hose product, in this order, is $\pi$.
References
[1] Goulden, I. P., Guay-Paquet, M., Novak, J. Monotone Hurwitz numbers in genus zero MathSciNet:3095005
Code
def statistic(mu):
return Hurwitz(mu) / mu.conjugacy_class_size()
def Hurwitz(alpha):
alpha = Partition(alpha)
d = alpha.size()
r = factorial(d) / prod(factorial(m) for m in alpha.to_exp()) * prod(binomial(2*p, p) for p in alpha)
k = len(alpha) - 3
if k >= 0:
return r * rising_factorial(2*d + 1, k)
return r / rising_factorial(2*d + k + 1, -k)
Created
Jan 01, 2024 at 23:37 by Martin Rubey
Updated
Aug 05, 2024 at 22:53 by Martin Rubey
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