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 A245902 #9 Jun 03 2018 03:40:34 %S A245902 1,2,7,37,222 %N A245902 Number of permutations of length 2n-1 avoiding 312 that can be realized on increasing binary trees. %C A245902 The number of permutations of length 2n-1 avoiding 312 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 A245902 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 A245902 Manda Riehl, <a href="/A245902/a245902.png">When n=3, the 7 permutations of length 5 that avoid 312 and can be realized on increasing binary trees.</a> %e A245902 For n=3, the a(3)= 7 permutations can be read from the sample trees given in the Links section above. %Y A245902 A245902 appears to be the terms of A245899 with odd indices. A245895 is the number of increasing unary-binary trees whose breadth-first reading word avoids 312. %K A245902 nonn,more %O A245902 1,2 %A A245902 _Manda Riehl_, Aug 22 2014