|
|
A331874
|
|
Number of semi-lone-child-avoiding locally disjoint rooted trees with n unlabeled leaves.
|
|
10
|
|
|
2, 3, 8, 24, 67, 214, 687, 2406, 8672, 32641, 125431, 493039, 1964611
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
A rooted tree is semi-lone-child-avoiding if there are no vertices with exactly one child unless the child is an endpoint/leaf.
Locally disjoint means no child of any vertex has branches overlapping the branches of any other (inequivalent) child of the same vertex.
|
|
LINKS
|
|
|
EXAMPLE
|
The a(1) = 2 through a(4) = 24 trees:
o (oo) (ooo) (oooo)
(o) (o(o)) (o(oo)) (o(ooo))
((o)(o)) (oo(o)) (oo(oo))
(o(o)(o)) (ooo(o))
(o(o(o))) ((oo)(oo))
((o)(o)(o)) (o(o(oo)))
(o((o)(o))) (o(oo(o)))
((o)((o)(o))) (oo(o)(o))
(oo(o(o)))
(o(o)(o)(o))
(o(o(o)(o)))
(o(o(o(o))))
(oo((o)(o)))
((o)(o)(o)(o))
((o(o))(o(o)))
((oo)((o)(o)))
(o((o)(o)(o)))
(o(o)((o)(o)))
(o(o((o)(o))))
((o)((o)(o)(o)))
((o)(o)((o)(o)))
(o((o)((o)(o))))
(((o)(o))((o)(o)))
((o)((o)((o)(o))))
|
|
MATHEMATICA
|
disjointQ[u_]:=Apply[And, Outer[#1==#2||Intersection[#1, #2]=={}&, u, u, 1], {0, 1}];
slaurt[n_]:=If[n==1, {o, {o}}, Join@@Table[Select[Union[Sort/@Tuples[slaurt/@ptn]], disjointQ[Select[#, !AtomQ[#]&]]&], {ptn, Rest[IntegerPartitions[n]]}]];
Table[Length[slaurt[n]], {n, 8}]
|
|
CROSSREFS
|
Not requiring local disjointness gives A050381.
The same trees counted by number of vertices are A331872.
The Matula-Goebel numbers of these trees are A331873.
Lone-child-avoiding rooted trees counted by leaves are A000669.
Semi-lone-child-avoiding rooted trees counted by vertices are A331934.
Cf. A000081, A001678, A300660, A316473, A316495, A316696, A331678, A331679, A331680, A331682, A331687, A331871, A331935.
|
|
KEYWORD
|
nonn,more
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|