This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A245894 #11 Sep 08 2014 08:46:49 %S A245894 1,2,14,163,2558 %N A245894 Number of labeled increasing binary trees on 2n-1 nodes whose breadth-first reading word avoids 231. %C A245894 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). %C A245894 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 A245894 Manda Riehl, <a href="/A245894/a245894.png">For n = 3: the 14 labeled trees on 5 nodes whose associated permutation avoids 231. </a> %e A245894 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. %Y A245894 A245888 gives the number of unary-binary trees instead of binary trees. %Y A245894 A245901 gives the number of permutations which avoid 231 that are breadth-first reading words on labeled increasing binary trees. %K A245894 nonn,more %O A245894 1,2 %A A245894 _Manda Riehl_, Aug 22 2014