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A054945
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Number of strongly connected labeled digraphs on n nodes with an odd number of edges.
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1
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0, 0, 8, 800, 282528, 367387328, 1761545807424, 31759604694829568, 2200205489188051284480, 595216852658907342647518208, 635231932478914399659212336569344, 2690533983413127566229805840755659706368, 45382894419701545228622064475653706685702246400, 3054532231410772852023213016232868881612380314752933888
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OFFSET
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1,3
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LINKS
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FORMULA
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MATHEMATICA
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b[n_] := b[n] = If[n == 1, 1, 2^(n*(n - 1)) - Sum[Binomial[n, j]*2^((n - 1)*(n - j))*b[j], {j, 1, n - 1}]];
c[1] = 1; c[n_] := c[n] = b[n] + Sum[Binomial[n - 1, j - 1]*b[n - j]*c[j], {j, 1, n - 1}];
a[n_] := (c[n] - (n - 1)!)/2;
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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