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A123544
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Number of connected labeled 2-regular relations of order n.
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5
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0, 0, 1, 6, 87, 1980, 66270, 3050460, 184716630, 14231775600, 1359481407480, 157694893448400, 21835679256606600, 3557942554594428000, 673941365091485290800, 146851484638349504613600
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OFFSET
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0,4
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REFERENCES
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R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1982.
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LINKS
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FORMULA
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MATHEMATICA
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m = 16;
a1499[n_] := (n - 1)*n!*Gamma[n - 1/2]*Hypergeometric1F1[2 - n, 3/2 - n, -1/2]/Sqrt[Pi];
egf = Log[1 + Sum[a1499[k] x^k/k!, {k, 1, m}]];
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PROG
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(PARI) seq(n)={Vec(serlaplace(log(serlaplace(exp(-x/2 + O(x*x^n))/sqrt(1-x + O(x*x^n))))), -(n+1))}; \\ Andrew Howroyd, Sep 09 2018
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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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