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 A245890 Number of labeled increasing unary-binary trees on n nodes whose breadth-first reading word avoids 321. 3
 1, 1, 3, 9, 37, 165, 834, 4515 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The number of labeled increasing unary-binary trees with an associated permutation avoiding 321 in the classical sense.  The tree's permutation is found by recording the labels in the order in which 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 Manda Riehl, The 9 trees when n=4. EXAMPLE When n=4, a(n)=9.  In the Links above we show the nine labeled increasing trees on four nodes whose permutation avoids 321. CROSSREFS A245896 gives the number of binary trees instead of unary-binary trees.  A245900 gives the number of permutations which avoid 321 that are breadth-first reading words on labeled increasing unary-binary trees. Sequence in context: A149022 A134818 A002751 * A119856 A077365 A319119 Adjacent sequences:  A245887 A245888 A245889 * A245891 A245892 A245893 KEYWORD nonn,more AUTHOR Manda Riehl, Aug 19 2014 STATUS approved

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Last modified November 18 09:23 EST 2018. Contains 317279 sequences. (Running on oeis4.)