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Search: id:A141268
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A141268 Number of phylogenetic rooted trees with n unlabeled objects. +0
2
1, 2, 4, 11, 30, 96, 308, 1052, 3648, 13003, 47006, 172605, 640662, 2402388, 9082538, 34590673, 132566826, 510904724, 1978728356, 7697565819 (list; graph; listen)
OFFSET

0,2

COMMENT

Unlabeled analog of A005804 = Phylogenetic trees with n labels.

LINKS

Thomas Wieder, Home Page.

Thomas Wieder, (Old) Home Page.

EXAMPLE

For n=4 we have A141268(4)=11 because

Set(Set(Z),Set(Z),Set(Z,Z)),

Set(Set(Z),Set(Set(Z),Set(Z,Z))),

Set(Z,Z,Z,Z),

Set(Set(Z,Z),Set(Z,Z)),

Set(Set(Set(Z),Set(Z)),Set(Z,Z)),

Set(Set(Z),Set(Z),Set(Set(Z),Set(Z))),

Set(Set(Z),Set(Z),Set(Z),Set(Z)),

Set(Set(Z),Set(Set(Z),Set(Z),Set(Z))),

Set(Set(Set(Z),Set(Z)),Set(Set(Z),Set(Z))),

Set(Set(Z),Set(Z,Z,Z)),

Set(Set(Z),Set(Set(Z),Set(Set(Z),Set(Z))))

MAPLE

combstruct command: A141268 := [H, {H=Union(Set(Z, card>=1), Set(H, card>=2))}, unlabelled]; seq(count(Test, size=j), j=1..20);

CROSSREFS

Cf. A005804.

Sequence in context: A007719 A148156 A148157 this_sequence A135527 A148158 A148159

Adjacent sequences: A141265 A141266 A141267 this_sequence A141269 A141270 A141271

KEYWORD

nonn

AUTHOR

Thomas Wieder (thomas.wieder(AT)t-online.de), Jun 20 2008

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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