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A215773
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Number of undirected labeled graphs on n+3 nodes with exactly n cycle graphs as connected components.
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2
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0, 3, 25, 120, 420, 1190, 2898, 6300, 12540, 23265, 40755, 68068, 109200, 169260, 254660, 373320, 534888, 750975, 1035405, 1404480, 1877260, 2475858, 3225750, 4156100, 5300100, 6695325, 8384103, 10413900, 12837720, 15714520, 19109640, 23095248, 27750800
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listen;
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internal format)
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: (8*x^2+4*x+3)*x/(1-x)^7.
a(n) = n*(n+1)*(n+2)*(n+3)*(n^2+n+4)/48.
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EXAMPLE
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a(1) = 3: .1-2. .1.2. .1-2.
. .|.|. .|X|. ..X..
. .3-4. .3.4. .3-4.
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MAPLE
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a:= n-> (24+(50+(41+(21+(7+n)*n)*n)*n)*n)*n/48:
seq (a(n), n=0..40);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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