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A304070
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Number of simple graphs with n vertices rooted at a pair of distinguished vertices.
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5
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0, 2, 8, 40, 240, 1992, 24416, 483040, 16343872, 982635280, 106979975168, 21285548190080, 7783083940331520, 5254164116114948480, 6577258363669088914432, 15332656940815954900371968, 66830735142688170751257497600, 546722015615195079134707942219904
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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The graphs do not need to be connected.
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LINKS
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FORMULA
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EXAMPLE
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a(3)=8: 1 for the graph with no edge, 3 for the graph with one edge, 3 for the graph with two edges, 1 for the triangle.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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