INRIA Algorithms Project, <a href="http://algoecs.inria.fr/ecsservices/ecsstructure?searchType=1&service=Search&searchTermsnbr=811">Encyclopedia of Combinatorial Structures 811</a>
editing
approved
nn=35; s[n_, k_]:=s[n, k]=a[n+1-k]+If[n<2k, 0, -s[n-k, k]]; a[1]=1; a[n_]:=a[n]=Sum[a[i]s[n-1, i]i, {i, 1, n-1}]/(n-1); it=Table[a[i], {i, 1, nn}]; CoefficientList[Series[Product[1/(1-x^i)^it[[i]], {i, 1, nn}], {x, 0, nn}], x] (* after code given by _Robert A. Russel_ Russell_ in A004111 *)
approved
editing
editing
approved
nn=35; s[n_, k_]:=s[n, k]=a[n+1-k]+If[n<2k, 0, -s[n-k, k]]; a[1]=1; a[n_]:=a[n]=Sum[a[i]s[n-1, i]i, {i, 1, n-1}]/(n-1); it=Table[a[i], {i, 1, nn}]; CoefficientList[Series[Product[1/(1-x^i)^it[[i]], {i, 1, nn}], {x, 0, nn}], x] (* after code given by _Robert A . Russel _ in A004111 *)
approved
editing
editing
approved
Alois P. Heinz, <a href="/A052843/b052843.txt">Table of n, a(n) for n = 0..1000</a>
# second Maple program:
with(numtheory):
b:= proc(n) option remember; `if`(n<2, n, add(b(n-k)*add(d*
b(d)*(-1)^(k/d+1), d=divisors(k)), k=1..n-1)/(n-1))
end:
a:= proc(n) option remember; `if`(n=0, 1, add(add(d*b(d),
d=divisors(j)) *a(n-j), j=1..n)/n)
end:
seq(a(n), n=0..40); # Alois P. Heinz, Mar 06 2015
Cf. A004111.
approved
editing
editing
approved
a(n) is the number of forests of rooted unlabeled identity trees. Euler tarnsform transform of A004111. - Geoffrey Critzer, Oct 13 2012
added Added more terms _, _Geoffrey Critzer_, Oct 13 2012
proposed
editing