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A355671
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Number of labeled trees on [n] that are bicentered.
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2
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0, 0, 1, 0, 12, 60, 570, 8190, 134456, 2408616, 49307670, 1159112130, 30619757652, 891045909468, 28244653953698, 969331283419590, 35858099428919280, 1423688804991442896, 60402176709135347502, 2726896792761748601226, 130498364319404393167820
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OFFSET
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0,5
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COMMENTS
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This is the labeled version of A000677 where pertinent definitions can be found.
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LINKS
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FORMULA
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MATHEMATICA
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nn = 20; T = NestList[z Exp[#] &, z, nn]; G[k_, z_] := T[[k + 1]];
H[k_, z_] := T[[k + 1]] - T[[k]]; H[0, z_] := z; ReplacePart[ Sum[Range[0, nn]! CoefficientList[Series[H[m, z]^2/2, {z, 0, nn}], z], {m, 1, nn/2 - 1}], 3 -> 1]
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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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