A320160 Number of series-reduced balanced rooted trees whose leaves form an integer partition of n.
1, 2, 3, 6, 9, 19, 31, 63, 110, 215, 391, 773, 1451, 2879, 5594, 11173, 22041, 44136, 87631, 175155, 348186, 694013, 1378911, 2743955, 5452833, 10853541, 21610732, 43122952, 86192274, 172753293, 347114772, 699602332, 1414033078, 2866580670, 5826842877, 11874508385
Offset: 1
Keywords
Examples
The a(1) = 1 through a(6) = 19 rooted trees: 1 2 3 4 5 6 (11) (12) (13) (14) (15) (111) (22) (23) (24) (112) (113) (33) (1111) (122) (114) ((11)(11)) (1112) (123) (11111) (222) ((11)(12)) (1113) ((11)(111)) (1122) (11112) (111111) ((11)(13)) ((11)(22)) ((12)(12)) ((11)(112)) ((12)(111)) ((11)(1111)) ((111)(111)) ((11)(11)(11))
Links
- Andrew Howroyd, Table of n, a(n) for n = 1..500
Crossrefs
Programs
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Mathematica
sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}]; mps[set_]:=Union[Sort[Sort/@(#/.x_Integer:>set[[x]])]&/@sps[Range[Length[set]]]]; phy2[labs_]:=If[Length[labs]==1,labs,Union@@Table[Sort/@Tuples[phy2/@ptn],{ptn,Select[mps[Sort[labs]],Length[#1]>1&]}]]; Table[Sum[Length[Select[phy2[ptn],SameQ@@Length/@Position[#,_Integer]&]],{ptn,IntegerPartitions[n]}],{n,8}]
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PARI
EulerT(v)={Vec(exp(x*Ser(dirmul(v,vector(#v,n,1/n))))-1, -#v)} seq(n)={my(u=vector(n, n, 1), v=vector(n)); while(u, v+=u; u=EulerT(u)-u); v} \\ Andrew Howroyd, Oct 25 2018
Extensions
Terms a(14) and beyond from Andrew Howroyd, Oct 25 2018
Comments