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A316694 Number of lone-child-avoiding locally disjoint rooted identity trees whose leaves form an integer partition of n. 15
1, 1, 2, 3, 6, 13, 28, 62, 143, 338, 804, 1948, 4789, 11886, 29796, 75316, 191702, 491040, 1264926, 3274594, 8514784, 22229481, 58243870 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

A rooted tree is lone-child-avoiding if every non-leaf node has at least two branches. It is locally disjoint if no branch overlaps any other (unequal) branch of the same root. It is an identity tree if no branch appears multiple times under the same root.

LINKS

Table of n, a(n) for n=1..23.

Gus Wiseman, Sequences counting series-reduced and lone-child-avoiding trees by number of vertices.

EXAMPLE

The a(7) = 28 rooted trees:

  7,

  (16),

  (25),

  (1(15)),

  (34),

  (1(24)), (2(14)), (4(12)), (124),

  (1(1(14))),

  (3(13)),

  (2(23)),

  (1(1(23))), (1(2(13))), (1(3(12))), (1(123)), (2(1(13))), (3(1(12))), (12(13)), (13(12)),

  (1(1(1(13)))),

  (2(2(12))),

  (1(1(2(12)))), (1(2(1(12)))), (1(12(12))), (2(1(1(12)))), (12(1(12))),

  (1(1(1(1(12))))).

Missing from this list but counted by A300660 are ((12)(13)) and ((12)(1(12))).

MATHEMATICA

disjointQ[u_]:=Apply[And, Outer[#1==#2||Intersection[#1, #2]=={}&, u, u, 1], {0, 1}];

nms[n_]:=nms[n]=Prepend[Join@@Table[Select[Union[Sort/@Tuples[nms/@ptn]], And[UnsameQ@@#, disjointQ[#]]&], {ptn, Rest[IntegerPartitions[n]]}], {n}];

Table[Length[nms[n]], {n, 10}]

CROSSREFS

Cf. A000081, A000669, A001678, A141268, A292504, A316653, A316654, A316656.

The semi-identity tree version is A212804.

Not requiring local disjointness gives A300660.

The non-identity tree version is A316696.

This is the case of A331686 where all leaves are singletons.

Rooted identity trees are A004111.

Locally disjoint rooted identity trees are A316471.

Lone-child-avoiding locally disjoint rooted trees are A331680.

Locally disjoint enriched identity p-trees are A331684.

Cf. A306200, A316697, A331678, A331679, A331681, A331683, A331783, A331874.

Sequence in context: A032143 A032160 A089735 * A000646 A316770 A197463

Adjacent sequences:  A316691 A316692 A316693 * A316695 A316696 A316697

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Jul 10 2018

EXTENSIONS

a(21)-a(23) from Robert Price, Sep 16 2018

Updated with corrected terminology by Gus Wiseman, Feb 06 2020

STATUS

approved

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Last modified January 25 15:54 EST 2021. Contains 340417 sequences. (Running on oeis4.)