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A330624 Number of non-isomorphic series-reduced rooted trees whose leaves are sets (not necessarily disjoint) with a total of n elements. 9
1, 1, 3, 10, 61, 410, 3630 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
A rooted tree is series-reduced if it has no unary branchings, so every non-leaf node covers at least two other nodes.
LINKS
EXAMPLE
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}}}
CROSSREFS
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.
Sequence in context: A009654 A013565 A156075 * A228773 A034889 A260969
KEYWORD
nonn,more
AUTHOR
Gus Wiseman, Dec 25 2019
STATUS
approved

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Last modified April 22 08:12 EDT 2024. Contains 371893 sequences. (Running on oeis4.)