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A330626 Number of non-isomorphic series/singleton-reduced rooted trees whose leaves are sets (not necessarily disjoint) with a total of n atoms. 8
1, 1, 1, 3, 17, 100, 755 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

A series/singleton-reduced rooted tree on a multiset m is either the multiset m itself or a sequence of series/singleton-reduced rooted trees, one on each part of a multiset partition of m that is neither minimal (all singletons) nor maximal (only one part).

LINKS

Table of n, a(n) for n=0..6.

EXAMPLE

Non-isomorphic representatives of the a(1) = 1 through a(4) = 17 trees:

  {1}  {1,2}  {1,2,3}      {1,2,3,4}

              {{1},{1,2}}  {{1},{1,2,3}}

              {{1},{2,3}}  {{1,2},{1,2}}

                           {{1,2},{1,3}}

                           {{1},{2,3,4}}

                           {{1,2},{3,4}}

                           {{1},{1},{1,2}}

                           {{1},{1},{2,3}}

                           {{1},{2},{1,2}}

                           {{1},{2},{1,3}}

                           {{1},{2},{3,4}}

                           {{1},{{1},{1,2}}}

                           {{1},{{1},{2,3}}}

                           {{1},{{2},{1,2}}}

                           {{1},{{2},{1,3}}}

                           {{1},{{2},{3,4}}}

                           {{2},{{1},{1,3}}}

CROSSREFS

The non-singleton-reduced version is A330624.

The generalization where leaves are multisets is A330470.

A labeled version is A330628 (strongly normal).

The case with all atoms distinct is A004114.

The balanced version is A330668.

Cf. A000669, A004111, A005804, A007716, A141268, A330465, A330625, A330627, A330654, A330663, A330677.

Sequence in context: A155610 A001541 A322242 * A161940 A074565 A241768

Adjacent sequences:  A330623 A330624 A330625 * A330627 A330628 A330629

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Dec 26 2019

STATUS

approved

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Last modified February 18 15:30 EST 2020. Contains 332019 sequences. (Running on oeis4.)