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A217436
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Triangular array read by rows. T(n,k) is the number of labeled relations on n elements with exactly k vertices of indegree and outdegree = 0.
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0
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1, 1, 1, 13, 2, 1, 469, 39, 3, 1, 63577, 1876, 78, 4, 1, 33231721, 317885, 4690, 130, 5, 1, 68519123173, 199390326, 953655, 9380, 195, 6, 1, 562469619451069, 479633862211, 697866141, 2225195, 16415, 273, 7, 1, 18442242396353040817, 4499756955608552, 1918535448844, 1860976376, 4450390, 26264, 364, 8, 1
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OFFSET
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0,4
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COMMENTS
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Row sums = 2^(n^2). First column (k = 0) is A173403.
Sum_{k=1,2,...,n} T(n,k)*k = A197927.
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LINKS
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FORMULA
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E.g.f.: exp(y*x)*A(x) where A(x) is the e.g.f. for A173403.
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EXAMPLE
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1,
1, 1,
13, 2, 1,
469, 39, 3, 1,
63577, 1876, 78, 4, 1,
33231721, 317885, 4690, 130, 5, 1,
68519123173, 199390326, 953655, 9380, 195, 6, 1
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MATHEMATICA
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nn=6; s=Sum[Sum[(-1)^k Binomial[n, k] 2^(n-k)^2, {k, 0, n}] x^n/n!, {n, 0, nn}]; Range[0, nn]! CoefficientList[Series[Exp[ y x] s, {x, 0, nn}], {x, y}] //Grid
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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