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A246566 Number of rooted ordered trees with n non-root nodes such that the branch lengths are weakly decreasing. 2
1, 1, 2, 4, 10, 24, 62, 155, 396, 992, 2504, 6228, 15512, 38220, 94059, 229498, 558642, 1350384, 3255138, 7801327, 18642118, 44329833, 105111283, 248184255, 584396849, 1371048495, 3208318247, 7483522231, 17413665881, 40405120865, 93543352492 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..30.

Joerg Arndt, All trees for 0 <= n <= 5

EXAMPLE

The a(3) = 4 such trees are:

:

:     1:

:    [ 1 1 1 ]

:    [ 0 0 0 ]

:

:  O--o

:  .--o

:  .--o

:

:

:     2:

:    [ 2 1 ]

:    [ 0 0 ]

:

:  O--o--o

:  .--o

:

:

:     3:

:    [ 2 1 ]

:    [ 0 1 ]

:

:  O--o--o

:     .--o

:

:

:     4:

:    [ 3 ]

:    [ 0 ]

:

:  O--o--o--o

:

See the Arndt link for all trees for 0 <= n <= 5.

CROSSREFS

Cf. A000108 (all trees), A246565 (ascending branch lengths), A193196, A192243, A001519.

Sequence in context: A006575 A307900 A230551 * A230553 A138175 A121691

Adjacent sequences:  A246563 A246564 A246565 * A246567 A246568 A246569

KEYWORD

nonn

AUTHOR

Joerg Arndt, Aug 30 2014

STATUS

approved

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Last modified April 13 05:48 EDT 2021. Contains 342935 sequences. (Running on oeis4.)