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A290689 Number of transitive rooted trees with n nodes. 72
1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 88, 143, 229, 370, 592, 955, 1527, 2457, 3929 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

A rooted tree is transitive if every proper terminal subtree is also a branch of the root. First differs from A206139 at a(13) = 143.

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

The a(7) = 8 trees are: (o(oooo)), (oo(ooo)), (o(o)((o))), (o(o)(oo)), (ooo(oo)), (oo(o)(o)), (oooo(o)), (oooooo).

MATHEMATICA

nn=18;

rtall[n_]:=If[n===1, {{}}, Module[{cas}, Union[Sort/@Join@@(Tuples[rtall/@#]&/@IntegerPartitions[n-1])]]];

Table[Length[Select[rtall[n], Complement[Union@@#, #]==={}&]], {n, nn}]

CROSSREFS

Cf. A000081, A004111, A279861, A290822.

Sequence in context: A206139 A023440 A225396 * A191869 A077373 A202278

Adjacent sequences:  A290686 A290687 A290688 * A290690 A290691 A290692

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Oct 19 2017

EXTENSIONS

a(20) from Robert Price, Sep 13 2018

STATUS

approved

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Last modified July 21 06:55 EDT 2019. Contains 325192 sequences. (Running on oeis4.)