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A050395
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Reversion of rooted trees A000081.
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2
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1, -1, 0, 1, -1, 1, -4, 11, -18, 18, 0, -60, 189, -360, 453, -373, 294, -652, 1443, -841, -6127, 27681, -75150, 172371, -389662, 867415, -1630604, 1826409, 1738343, -15855044, 49812000, -109702703, 186277940, -229343877, 86783346, 618570769, -2635628596
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listen;
history;
text;
internal format)
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OFFSET
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1,7
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LINKS
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MATHEMATICA
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Module[{t}, t[1] = 1; t[k_] := t[k] = Sum[DivisorSum[k - m, t[#] # &] t[m]/(k-1), {m, k-1}]; InverseSeries[Sum[t[n] x^n, {n, 1, 40}] + O[x]^41][[3]]] (* Vladimir Reshetnikov, Nov 03 2015 *)
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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