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 A245901 #9 Jun 03 2018 03:40:29 %S A245901 1,2,10,74,667 %N A245901 Number of permutations of length 2n-1 avoiding 231 that can be realized on increasing binary trees. %C A245901 The number of permutations of length 2n-1 avoiding 231 in the classical sense which can be realized as labels on an increasing binary tree read in the order they appear in a breadth-first search. (Note that breadth-first search reading word is equivalent to reading the tree left to right by levels, starting with the root.) %C A245901 In some cases, more than one tree results in the same breadth-first search reading word, but here we count the permutations, not the trees. %H A245901 Manda Riehl, <a href="/A245901/a245901.png">When n=3, the 10 permutations of length 5 that avoid 231 and can be realizeed on increasing binary trees. </a> %e A245901 For n=3, the a(3)= 10 permutations can be read from the sample trees given in the Links section above. %Y A245901 A245901 appears to be the terms of A245898 with odd indices. A245894 is the number of increasing unary-binary trees whose breadth-first reading word avoids 231. %K A245901 nonn,more %O A245901 1,2 %A A245901 _Manda Riehl_, Aug 22 2014