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A356941
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Number of multiset partitions of integer partitions of n such that all blocks are gapless.
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7
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1, 1, 3, 6, 13, 24, 49, 88, 166, 297, 534, 932, 1635, 2796, 4782, 8060, 13521, 22438, 37080, 60717, 98979, 160216, 258115, 413382, 659177, 1045636, 1651891, 2597849, 4069708, 6349677, 9871554, 15290322, 23604794, 36318256, 55705321, 85177643, 129865495
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OFFSET
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0,3
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COMMENTS
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A multiset is gapless if it covers an interval of positive integers. For example, {2,3,3,4} is gapless but {1,1,3,3} is not.
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LINKS
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FORMULA
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EXAMPLE
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The a(1) = 1 through a(4) = 13 multiset partitions:
{{1}} {{2}} {{3}} {{4}}
{{1,1}} {{1,2}} {{2,2}}
{{1},{1}} {{1,1,1}} {{1,1,2}}
{{1},{2}} {{1},{3}}
{{1},{1,1}} {{2},{2}}
{{1},{1},{1}} {{1,1,1,1}}
{{1},{1,2}}
{{2},{1,1}}
{{1},{1,1,1}}
{{1,1},{1,1}}
{{1},{1},{2}}
{{1},{1},{1,1}}
{{1},{1},{1},{1}}
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MATHEMATICA
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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]]]];
nogapQ[m_]:=Or[m=={}, Union[m]==Range[Min[m], Max[m]]];
Table[Length[Select[Join@@mps/@IntegerPartitions[n], And@@nogapQ/@#&]], {n, 0, 5}]
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PROG
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(PARI) \\ Here G(n) gives A034296 as vector
G(N) = Vec(sum(n=1, N, x^n/(1-x^n) * prod(k=1, n-1, 1+x^k+O(x*x^(N-n))) ));
seq(n) = {my(u=G(n)); Vec(1/prod(k=1, n-1, (1 - x^k + O(x*x^n))^u[k])) } \\ Andrew Howroyd, Dec 30 2022
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CROSSREFS
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A011782 counts multisets covering an initial interval.
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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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