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A330624
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Number of non-isomorphic series-reduced rooted trees whose leaves are sets (not necessarily disjoint) with a total of n elements.
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9
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OFFSET
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0,3
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COMMENTS
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A rooted tree is series-reduced if it has no unary branchings, so every non-leaf node covers at least two other nodes.
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LINKS
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EXAMPLE
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Non-isomorphic representatives of the a(1) = 1 through a(3) = 10 trees:
{1} {1,2} {1,2,3}
{{1},{1}} {{1},{1,2}}
{{1},{2}} {{1},{2,3}}
{{1},{1},{1}}
{{1},{1},{2}}
{{1},{2},{3}}
{{1},{{1},{1}}}
{{1},{{1},{2}}}
{{1},{{2},{3}}}
{{2},{{1},{1}}}
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CROSSREFS
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The version with multisets as leaves is A330465.
The singleton-reduced case is A330626.
A labeled version is A330625 (strongly normal).
The case with all atoms distinct is A141268.
The case where all leaves are singletons is A330470.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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