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A330676
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Number of balanced reduced multisystems of weight n and maximum depth whose atoms cover an initial interval of positive integers.
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9
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1, 1, 2, 8, 70, 1012, 21944, 665708, 26917492, 1399033348, 90878863352, 7214384973908, 687197223963640, 77354805301801012, 10158257981179981304, 1539156284259756811748, 266517060496258245459352, 52301515332984084095078308, 11546416513975694879642736152
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OFFSET
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0,3
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COMMENTS
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A balanced reduced multisystem is either a finite multiset, or a multiset partition with at least two parts, not all of which are singletons, of a balanced reduced multisystem. The weight of an atom is 1, while the weight of a multiset is the sum of weights of its elements.
A finite multiset is normal if it covers an initial interval of positive integers.
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LINKS
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EXAMPLE
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The a(0) = 1 through a(3) = 8 multisystems:
{} {1} {1,1} {{1},{1,1}}
{1,2} {{1},{1,2}}
{{1},{2,2}}
{{1},{2,3}}
{{2},{1,1}}
{{2},{1,2}}
{{2},{1,3}}
{{3},{1,2}}
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MATHEMATICA
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allnorm[n_]:=If[n<=0, {{}}, Function[s, Array[Count[s, y_/; y<=#]+1&, n]]/@Subsets[Range[n-1]+1]];
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]]]];
totm[m_]:=Prepend[Join@@Table[totm[p], {p, Select[mps[m], 1<Length[#]<Length[m]&]}], m];
Table[Sum[Length[Select[totm[m], Depth[#]==If[n<=1, 2, n]&]], {m, allnorm[n]}], {n, 5}]
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PROG
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(PARI) EulerT(v)={Vec(exp(x*Ser(dirmul(v, vector(#v, n, 1/n))))-1, -#v)}
R(n, k)={my(v=vector(n), u=vector(n)); v[1]=k; for(n=1, #v, for(i=n, #v, u[i] += v[i]*(-1)^(i-n)*binomial(i-1, n-1)); v=EulerT(v)); u}
seq(n)={concat([1], sum(k=1, n, R(n, k)*sum(r=k, n, binomial(r, k)*(-1)^(r-k))))} \\ Andrew Howroyd, Dec 30 2020
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CROSSREFS
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The case with all atoms equal is A000111.
The case with all atoms different is A006472.
The version allowing all depths is A330655.
The version where the atoms are the prime indices of n is A330665.
The strongly normal version is A330675.
The version where the degrees are the prime indices of n is A330728.
Multiset partitions of normal multisets are A255906.
Series-reduced rooted trees with normal leaves are A316651.
Cf. A000669, A001055, A005121, A005804, A318812, A330469, A330474, A330654, A330664, A330677, A330679.
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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