|
%I #8 Mar 18 2018 15:33:18
%S 1,1,3,8,29,110,469,2119
%N Number of labeled increasing unary-binary trees on n nodes whose breadth-first reading word avoids 312.
%C The number of labeled increasing unary-binary trees with an associated permutation avoiding 312 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.)
%C 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.
%H Manda Riehl, <a href="/A245889/a245889.png">The 8 trees when n = 4.</a>
%e When n=4, a(n)=8. In the Links above we show the eight labeled increasing trees on four nodes whose permutation avoids 312.
%Y A245895 gives the number of binary trees instead of unary-binary trees. A245899 gives the number of permutations which avoid 312 that are breadth-first reading words on labeled increasing unary-binary trees.
%K nonn,more
%O 1,3
%A _Manda Riehl_, Aug 18 2014
| 