OFFSET
1,7
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
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 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Christian G. Bower, Nov 15 1999
STATUS
approved