A253244 - OEIS

The OEIS is supported by the many generous donors to the OEIS Foundation.

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Other ways to Give

A253244

Number of unlabeled rooted trees with n nodes where the outdegrees (branching factors) of at least one pair of adjacent nodes differ by at least two and the outdegrees of at least one pair of adjacent nodes are equal.

0, 0, 0, 0, 0, 3, 9, 23, 65, 186, 507, 1380, 3764, 10270, 28001, 76568, 209749, 575900, 1584769, 4371279, 12083764, 33477190, 92939305, 258537475, 720575302, 2012021934, 5627886815, 15768237664, 44249863373, 124365487416, 350038837208, 986579529425

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,6

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..400

Index entries for sequences related to rooted trees

Index entries for sequences related to trees

FORMULA

a(n) = A000081(n) - A260353(n) - A260403(n) + A257654(n).

EXAMPLE

a(5) = 3:

: o o o