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A055350
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Number of labeled mobiles (circular rooted trees) with n nodes and 3 leaves.
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2
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8, 220, 4200, 71400, 1176000, 19474560, 330220800, 5787936000, 105380352000, 1997835840000, 39477236198400, 813155511168000, 17453093898240000, 390070546145280000, 9070029416448000000, 219204470936715264000
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OFFSET
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4,1
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LINKS
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MATHEMATICA
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m = 20;
L[x_] = Log[1-x] + O[x]^m // Normal;
A[_] = 0;
Do[A[x_] = x y - x L[A[x]] + O[x]^k // Normal // Expand, {k, m}];
Drop[(SeriesCoefficient[#, {y, 0, 3}]& /@ CoefficientList[A[x], x]) * Range[0, m-1]!, 4] (* Jean-François Alcover, Nov 01 2019 *)
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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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