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 A098543 #3 Mar 30 2012 18:36:43 %S A098543 1,4,12,44,236,2028,29164,719340,30943724,2350770668,318680099308, %T A098543 77793540073964,34472347123476972,27928291976711924204, %U A098543 41631598900551078537708,114829789064202679162399212 %N A098543 Column 2 of triangle A098542, which shifts left and up under the matrix square. %C A098543 Related to A002449, the number of different types of binary trees of height n. %F A098543 G.f.: A(x) = x*(1+x)/(1-x)*(G002449(x)-1), where G002449(x) is g.f. of A002449. %Y A098543 Cf. A002449, A098542, A098544. %K A098543 nonn %O A098543 2,2 %A A098543 _Paul D. Hanna_, Sep 16 2004