

A277795


Number of trees with n unlabeled nodes such that all nodes with degree >2 lie on a single path with length equal to the tree's diameter.


2



1, 1, 1, 1, 2, 3, 6, 11, 23, 47, 103, 223, 503, 1132, 2602, 5986, 13922, 32433, 75994, 178354, 419945, 990134, 2339033, 5531459
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OFFSET

0,5


COMMENTS

First differs from A000055 at a(10).
First differs from A130131 at a(10), n >= 1.
The ratio of consecutive terms seems to tend to some limit.  Andrey Zabolotskiy, Dec 12 2016


LINKS

Table of n, a(n) for n=0..23.
Andrey Zabolotskiy, Python script for the sequence


EXAMPLE

From Andrey Zabolotskiy, Nov 21 2016: (Start)
Three trees that are counted in A000055(10) but not in a(10):
(1)
o ooo
 
oo
 
o ooo
(2)
ooo

oooo

ooo
(3)
ooooooo

ooo
(End)


CROSSREFS

Cf. A000055, A130131.
Sequence in context: A274937 A199142 A090344 * A198662 A198620 A198648
Adjacent sequences: A277792 A277793 A277794 * A277796 A277797 A277798


KEYWORD

nonn,more


AUTHOR

Gabriel Burns, Oct 31 2016


EXTENSIONS

Corrections and more terms from Andrey Zabolotskiy, Nov 21 2016


STATUS

approved



