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A245894 Number of labeled increasing binary trees on 2n-1 nodes whose breadth-first reading word avoids 231. 8
1, 2, 14, 163, 2558 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The number of labeled increasing binary trees with an associated permutation avoiding 231 in the classical sense. The tree’s permutation is found by recording the labels in the order they appear in a breadth-first search. (Note that a breadth-first search reading word is equivalent to reading the tree labels left to right by levels, starting with the root).
In some cases, the same breadth-first search reading permutation can be found on differently shaped trees. This sequence gives the number of trees, not the number of permutations.
LINKS
EXAMPLE
When n=3, a(n)=14. In the Links above we show the fourteen labeled increasing binary trees on five nodes whose permutation avoids 231.
CROSSREFS
A245888 gives the number of unary-binary trees instead of binary trees.
A245901 gives the number of permutations which avoid 231 that are breadth-first reading words on labeled increasing binary trees.
Sequence in context: A364398 A074635 A201465 * A277362 A209937 A245896
KEYWORD
nonn,more
AUTHOR
Manda Riehl, Aug 22 2014
STATUS
approved

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Last modified March 19 01:57 EDT 2024. Contains 370952 sequences. (Running on oeis4.)