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A339038
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Number of unlabeled connected loopless multigraphs with n edges rooted at one unoriented edge.
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5
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1, 2, 7, 23, 88, 339, 1396, 5915, 26080, 118539, 555678, 2678458, 13262193, 67353325, 350493424, 1866989802, 10171394388, 56631507822, 322011612423, 1868702977253, 11061267210030, 66745602611831, 410360493588788, 2569318971123439, 16374787277199728, 106180292431149021
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OFFSET
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1,2
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LINKS
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FORMULA
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G.f.: x*f(x)/g(x) where f(x) is the g.f. of A339066 and g(x) is the g.f. of A050535.
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MATHEMATICA
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seq[n_] := (G[2n, x + O[x]^n, {1, 1}] + G[2n, x + O[x]^n, {2}])/G[2n, x + O[x]^n, {}] // CoefficientList[#/2, x]&;
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PROG
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seq(n)={my(A=O(x*x^n)); Vec((G(2*n, x+A, [1, 1]) + G(2*n, x+A, [2]))/G(2*n, x+A, []))/2}
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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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