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Identifier
Values
=>
Cc0020;cc-rep
([],1)=>1 ([],2)=>2 ([(0,1)],2)=>1 ([],3)=>6 ([(1,2)],3)=>5 ([(0,2),(1,2)],3)=>2 ([(0,1),(0,2),(1,2)],3)=>1 ([],4)=>24 ([(2,3)],4)=>22 ([(1,3),(2,3)],4)=>16 ([(0,3),(1,3),(2,3)],4)=>6 ([(0,3),(1,2)],4)=>18 ([(0,3),(1,2),(2,3)],4)=>8 ([(1,2),(1,3),(2,3)],4)=>10 ([(0,3),(1,2),(1,3),(2,3)],4)=>2 ([(0,2),(0,3),(1,2),(1,3)],4)=>2 ([(0,2),(0,3),(1,2),(1,3),(2,3)],4)=>1 ([(0,1),(0,2),(0,3),(1,2),(1,3),(2,3)],4)=>1 ([],5)=>120 ([(3,4)],5)=>114 ([(2,4),(3,4)],5)=>96 ([(1,4),(2,4),(3,4)],5)=>66 ([(0,4),(1,4),(2,4),(3,4)],5)=>24 ([(1,4),(2,3)],5)=>98 ([(1,4),(2,3),(3,4)],5)=>68 ([(0,1),(2,4),(3,4)],5)=>74 ([(2,3),(2,4),(3,4)],5)=>74 ([(0,4),(1,4),(2,3),(3,4)],5)=>32 ([(1,4),(2,3),(2,4),(3,4)],5)=>42 ([(0,4),(1,4),(2,3),(2,4),(3,4)],5)=>7 ([(1,3),(1,4),(2,3),(2,4)],5)=>34 ([(0,4),(1,2),(1,3),(2,4),(3,4)],5)=>8 ([(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>21 ([(0,4),(1,3),(2,3),(2,4),(3,4)],5)=>12 ([(0,4),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,3),(0,4),(1,3),(1,4),(2,3),(2,4)],5)=>2 ([(0,3),(0,4),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>1 ([(0,4),(1,3),(2,3),(2,4)],5)=>42 ([(0,1),(2,3),(2,4),(3,4)],5)=>46 ([(0,3),(1,2),(1,4),(2,4),(3,4)],5)=>16 ([(0,3),(0,4),(1,2),(1,4),(2,4),(3,4)],5)=>3 ([(0,3),(0,4),(1,2),(1,4),(2,3)],5)=>20 ([(0,1),(0,4),(1,3),(2,3),(2,4),(3,4)],5)=>2 ([(0,3),(0,4),(1,2),(1,4),(2,3),(2,4),(3,4)],5)=>1 ([(0,4),(1,2),(1,3),(2,3),(2,4),(3,4)],5)=>3 ([(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>17 ([(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>2 ([(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>1 ([(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4)],5)=>1 ([(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,4),(3,4)],5)=>1 ([(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>1 ([(0,1),(0,2),(0,3),(0,4),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4)],5)=>1 ([],6)=>720 ([(4,5)],6)=>696 ([(3,5),(4,5)],6)=>624 ([(2,5),(3,5),(4,5)],6)=>504 ([(1,5),(2,5),(3,5),(4,5)],6)=>336 ([(0,5),(1,5),(2,5),(3,5),(4,5)],6)=>120 ([(2,5),(3,4)],6)=>628 ([(2,5),(3,4),(4,5)],6)=>508 ([(1,2),(3,5),(4,5)],6)=>520 ([(3,4),(3,5),(4,5)],6)=>528 ([(1,5),(2,5),(3,4),(4,5)],6)=>352 ([(0,1),(2,5),(3,5),(4,5)],6)=>372 ([(2,5),(3,4),(3,5),(4,5)],6)=>388 ([(0,5),(1,5),(2,5),(3,4),(4,5)],6)=>156 ([(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>221 ([(0,5),(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>33 ([(2,4),(2,5),(3,4),(3,5)],6)=>356 ([(0,5),(1,5),(2,4),(3,4)],6)=>400 ([(1,5),(2,3),(2,4),(3,5),(4,5)],6)=>196 ([(0,5),(1,5),(2,3),(3,4),(4,5)],6)=>220 ([(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>270 ([(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>228 ([(0,5),(1,5),(2,4),(3,4),(4,5)],6)=>184 ([(0,5),(1,5),(2,3),(2,4),(3,5),(4,5)],6)=>36 ([(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>123 ([(0,5),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>65 ([(0,5),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>7 ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>68 ([(0,5),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>72 ([(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>4 ([(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>46 ([(0,5),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>14 ([(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,5),(1,4),(2,3)],6)=>534 ([(1,5),(2,4),(3,4),(3,5)],6)=>372 ([(0,1),(2,5),(3,4),(4,5)],6)=>394 ([(1,2),(3,4),(3,5),(4,5)],6)=>392 ([(0,5),(1,4),(2,3),(3,5),(4,5)],6)=>214 ([(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>238 ([(0,1),(2,5),(3,4),(3,5),(4,5)],6)=>254 ([(0,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>79 ([(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>133 ([(0,5),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>11 ([(1,4),(1,5),(2,3),(2,5),(3,4)],6)=>220 ([(0,5),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>66 ([(1,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>96 ([(0,5),(1,2),(1,4),(2,3),(3,5),(4,5)],6)=>106 ([(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>126 ([(0,5),(1,4),(2,3),(3,4),(3,5),(4,5)],6)=>90 ([(0,5),(1,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>6 ([(0,5),(1,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>21 ([(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>53 ([(0,5),(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,4),(2,3),(2,4),(3,5)],6)=>258 ([(0,1),(2,4),(2,5),(3,4),(3,5)],6)=>242 ([(0,5),(1,5),(2,3),(2,4),(3,4)],6)=>273 ([(0,4),(1,2),(1,3),(2,5),(3,5),(4,5)],6)=>98 ([(0,4),(1,2),(1,5),(2,5),(3,4),(3,5)],6)=>139 ([(0,4),(1,2),(2,5),(3,4),(3,5),(4,5)],6)=>114 ([(0,1),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>143 ([(0,4),(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>101 ([(0,3),(0,4),(1,2),(1,5),(2,5),(3,5),(4,5)],6)=>10 ([(0,3),(1,4),(1,5),(2,4),(2,5),(3,5),(4,5)],6)=>32 ([(0,4),(1,2),(1,5),(2,5),(3,4),(3,5),(4,5)],6)=>32 ([(0,1),(0,5),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>210 ([(0,5),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>12 ([(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>81 ([(0,5),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>7 ([(0,1),(0,5),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>16 ([(0,3),(0,5),(1,3),(1,5),(2,4),(2,5),(3,4),(4,5)],6)=>1 ([(0,3),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,5),(1,4),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>2 ([(0,1),(0,5),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>30 ([(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>9 ([(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,4),(0,5),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,5),(1,3),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>6 ([(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>34 ([(0,5),(1,3),(1,4),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>2 ([(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>27 ([(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,2),(1,3),(2,5),(3,4)],6)=>156 ([(0,3),(0,5),(1,2),(1,5),(2,4),(3,4),(4,5)],6)=>15 ([(0,5),(1,2),(1,4),(2,3),(3,4),(3,5),(4,5)],6)=>24 ([(0,1),(0,2),(1,5),(2,4),(3,4),(3,5),(4,5)],6)=>45 ([(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>36 ([(0,5),(1,3),(1,4),(2,4),(2,5),(3,4),(3,5)],6)=>19 ([(0,1),(0,5),(1,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(1,3),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>5 ([(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(2,4),(2,5),(3,4),(3,5)],6)=>2 ([(0,5),(1,2),(1,3),(1,4),(2,3),(2,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,5),(1,2),(1,3),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>26 ([(0,5),(1,3),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,2),(1,4),(2,3),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5)],6)=>2 ([(0,1),(0,2),(0,3),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(2,3),(4,5)],6)=>164 ([(0,2),(1,4),(1,5),(2,3),(3,4),(3,5),(4,5)],6)=>50 ([(0,1),(0,5),(1,5),(2,3),(2,4),(3,4),(4,5)],6)=>54 ([(0,1),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>101 ([(0,1),(0,5),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>5 ([(0,1),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>25 ([(0,1),(0,5),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,4),(0,5),(1,2),(1,3),(2,3),(2,5),(3,4),(4,5)],6)=>6 ([(0,4),(0,5),(1,2),(1,3),(1,4),(2,3),(2,5),(3,5),(4,5)],6)=>1 ([(0,3),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>3 ([(0,3),(0,5),(1,2),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,1),(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,3),(0,5),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(2,5),(3,4)],6)=>2 ([(0,1),(0,5),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>6 ([(0,3),(0,4),(1,2),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,3),(2,5),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,3),(2,5),(3,4)],6)=>2 ([(0,1),(0,3),(0,5),(1,2),(1,4),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>1 ([(0,1),(0,4),(0,5),(1,3),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,2),(0,5),(1,3),(1,4),(1,5),(2,3),(2,4),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,5),(1,2),(1,3),(1,4),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>26 ([(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>2 ([(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,1),(0,4),(0,5),(1,2),(1,3),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,5),(4,5)],6)=>1 ([(0,2),(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5)],6)=>1 ([(0,2),(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,2),(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1 ([(0,1),(0,2),(0,3),(0,4),(0,5),(1,2),(1,3),(1,4),(1,5),(2,3),(2,4),(2,5),(3,4),(3,5),(4,5)],6)=>1
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Description
The number of connected components of the friends and strangers graph.
Let $X$ and $Y$ be graphs with the same vertex set $\{1,\dots,n\}$. Then the friends-and-strangers graph has as vertex set the set of permutations $\mathfrak S_n$ and edges $\left(\sigma, (i, j)\circ\sigma\right)$ if $(i, j)$ is an edge of $X$ and $\left(\sigma(i), \sigma(j)\right)$ is an edge of $Y$.
This statistic is the number of connected components of the friends and strangers graphs where $X=Y$.
For example, if $X$ is a complete graph the statistic is $1$, if $X$ has no edges, the statistic is $n!$, and if $X$ is the path graph, the statistic is
$$ \sum_{k=0}^{\lfloor n/2\rfloor} (-1)^k (n-k)!\binom{n-k}{k}, $$
see [thm. 2.2, 3].
References
[1] Defant, C., Kravitz, N. Friends and Strangers Walking on Graphs arXiv:2009.05040
[2] Alon, N., Defant, C., Kravitz, N. Typical and Extremal Aspects of Friends-and-Strangers Graphs arXiv:2009.07840
[3] Stanley, R. P. An equivalence relation on the symmetric group and multiplicity-free flag $h$-vectors MathSciNet:3029438
Code
def FS(X, Y):
    n = X.num_verts()
    assert n == Y.num_verts()
    X = X.relabel(inplace=False)
    Y = Y.relabel(inplace=False)
    V = list(Permutations(n))
    E = []
    for pi in V:
        for i, j in X.edges(labels=False):
            a, b = pi[i], pi[j]
            if Y.has_edge(a-1, b-1):
                pi1 = list(pi)
                pi1[i], pi1[j] = b, a
                pi1 = Permutation(pi1)
                E.append((pi, pi1))
    return Graph([V, E]).copy(immutable=True)


def statistic(G):
    return FS(G, G).connected_components_number()
Created
Jan 21, 2022 at 17:44 by Martin Rubey
Updated
Jan 21, 2022 at 17:44 by Martin Rubey