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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.
4
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
OFFSET
0,6
FORMULA
a(n) = A000081(n) - A260353(n) - A260403(n) + A257654(n).
EXAMPLE
a(5) = 3:
: o o o
: | / \ / \
: o o o o o
: | | / \
: o o o o
: / \ |
: o o o
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 26 2015
STATUS
approved