A050395 Reversion of rooted trees A000081.
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
Offset: 1
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..100
- M. Drmota, B. Gittenberger, The shape of unlabeled rooted random trees, Eur. J. Comb. 31 (2010) no 8, 2028-2063, Remark.
- N. J. A. Sloane, Transforms
- Index entries for reversions of series
- Index entries for sequences related to rooted trees
Programs
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Mathematica
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 *)