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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
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
KEYWORD
nonn
AUTHOR
Joerg Arndt, Aug 30 2014
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)