A052120 Number of 3-valent trees (= boron trees or binary trees) with n nodes.

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

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Comments

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

Links

• 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.