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A322700
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Number of unlabeled graphs with loops spanning n vertices.
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31
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1, 1, 4, 14, 70, 454, 4552, 74168, 2129348, 111535148, 10812483376, 1945437208224, 650378721156736, 404749938336404704, 470163239887698967104, 1022592854829028311090816, 4177826139658552046627175072, 32163829440870460348768023969632
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OFFSET
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0,3
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COMMENTS
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The span of a graph is the union of its edges. The not necessarily spanning case is A000666.
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LINKS
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FORMULA
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MATHEMATICA
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Table[Sum[2^PermutationCycles[Ordering[Map[Sort, Select[Tuples[Range[n], 2], OrderedQ]/.Rule@@@Table[{i, prm[[i]]}, {i, n}], {1}]], Length], {prm, Permutations[Range[n]]}]/n!, {n, 0, 8}]//Differences (* Mathematica 8.0+ *)
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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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