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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)



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.


Table of n, a(n) for n=1..5.

Manda Riehl, For n = 3: the 14 labeled trees on 5 nodes whose associated permutation avoids 231.


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.


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: A052112 A074635 A201465 * A277362 A209937 A245896

Adjacent sequences:  A245891 A245892 A245893 * A245895 A245896 A245897




Manda Riehl, Aug 22 2014



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Last modified June 28 04:43 EDT 2017. Contains 288813 sequences.