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A052120 Number of 3-valent trees (= boron trees or binary trees) with n nodes. 1
1, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 4, 0, 6, 0, 11, 0, 18, 0, 37, 0, 66, 0, 135, 0, 265, 0, 552, 0, 1132, 0, 2410, 0, 5098, 0, 11020, 0, 23846, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,10

COMMENTS

Trees with n nodes each of valency either 1 or 3.

LINKS

Table of n, a(n) for n=1..41.

Eric Weisstein's World of Mathematics, Cayley Tree.

Eric Weisstein's World of Mathematics, Trivalent Tree

Index entries for sequences related to trees

CROSSREFS

See A000672, the subsequence of even-numbered terms, which is the main entry for this sequence, for more terms, references, etc.

Sequence in context: A201863 A035385 A051629 * A179461 A238763 A029186

Adjacent sequences:  A052117 A052118 A052119 * A052121 A052122 A052123

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified October 23 08:17 EDT 2014. Contains 248430 sequences.