A052893 Number of objects generated by the Combstruct grammar defined in the Maple program. See the link for the grammar specification.
1, 1, 3, 10, 37, 144, 589, 2483, 10746, 47420, 212668, 966324, 4439540, 20587286, 96237484, 453012296, 2145478716, 10215922013, 48877938369, 234862013473, 1132902329028, 5483947191651, 26630419098206, 129696204701807, 633339363924611, 3100369991303297
Offset: 0
Examples
From _Gus Wiseman_, Aug 02 2018: (Start) The a(3) = 10 free pure symmetric multifunctions with 4 unlabeled leaves: o[o[o[o]]] o[o[o][o]] o[o][o[o]] o[o[o]][o] o[o][o][o] o[o[o,o]] o[o,o[o]] o[o][o,o] o[o,o][o] o[o,o,o] (End)
Links
- Alois P. Heinz, Table of n, a(n) for n = 0..1000
- INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 869
- Maplesoft, Combstruct grammars.
- Mathematica Reference, Orderless.
Programs
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Maple
spec := [S, {C = Set(B,1 <= card), B=Prod(Z,S), S=Sequence(C)}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..20);
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Mathematica
multing[t_,n_]:=Array[(t+#-1)/#&,n,1,Times]; a[n_]:=a[n]=If[n==1,1,Sum[a[k]*Sum[Product[multing[a[First[s]],Length[s]],{s,Split[p]}],{p,IntegerPartitions[n-k]}],{k,1,n-1}]]; Array[a,30] (* Gus Wiseman, Aug 02 2018 *)
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PARI
EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)} seq(n)={my(v=[1]); for(n=1, n, v=Vec(1/(1-x*Ser(EulerT(v))))); v} \\ Andrew Howroyd, Aug 09 2020
Formula
G.f.: 1/(1 - g(x)) where g(x) is the g.f. of A052891. - Andrew Howroyd, Aug 09 2020
Extensions
More terms from Gus Wiseman, Aug 02 2018
Comments