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 A011272 #11 Apr 02 2015 17:29:13 %S A011272 0,1,3,13,64,339,1885,10851,64109,386510,2368354,14706331,92337618, %T A011272 585239903,3739309053,24059542845,155756019048,1013801283133, %U A011272 6630587014935,43553555324502 %N A011272 Hybrid binary rooted trees with n nodes whose root is labeled by "a". %H A011272 Nancy S. S. Gu, Nelson Y. Li, and Toufik Mansour, <a href="http://dx.doi.org/10.1016/j.disc.2007.04.007">2-Binary trees: bijections and related issues</a>, Discr. Math., 308 (2008), 1209-1221. %H A011272 J. M. Pallo, <a href="http://dx.doi.org/10.1080/00207169408804251">On the listing and random generation of hybrid binary trees</a>, International Journal of Computer Mathematics, 50 (1994) 135-145. %H A011272 <a href="/index/Ro#rooted">Index entries for sequences related to rooted trees</a> %F A011272 a(n) = A007863(n) - A011270(n). %K A011272 nonn %O A011272 0,3 %A A011272 Jean Pallo (pallo(AT)u-bourgogne.fr)