OFFSET
0,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..500
EXAMPLE
There are two trees for a(4):
o o o
| | |
o---o---o o----o
| | |
o o o
The first of these can have the 4 leaves colored in 5 indistinguishable ways and the second can have the 4 leaves colored in 6 indistinguishable ways so a(4) = 5 + 6 = 11.
PROG
(PARI) U(25, 2) \\ See A339779 for U(n, k).
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Dec 16 2020
STATUS
approved