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 A067294 #4 Mar 31 2012 13:20:06 %S A067294 5,9,23,66,202,645,2123,7150,24518,85306,300390,1068484,3833364, %T A067294 13855085,50401395,184392150,677998830,2504191470,9286661010, %U A067294 34564913820,129077071500,483474711330,1815928888254 %N A067294 Third column of triangle A028364. %C A067294 The first two columns give: A000108 (Catalan) and A005807. The next two columns give: A067295-6. %F A067294 a(n)= A028364(n+2, 2) = C(0)*C(n+2)+C(1)*C(n+1)+C(2)*C(n), with the Catalan numbers C(n)=A000108(n). a(n)= ((11*n^2+28*n+15)/(2*(2*n+1)*(2*n+3)))*C(n+2). %F A067294 G.f.: (c2(x)*c(x)-(c2(x)-1)/x)/x^2, with c2(x) := 1+x+2*x^2 and c(x) G.f. for Catalan numbers A000108. %Y A067294 First differences are in A071747. %K A067294 nonn,easy %O A067294 0,1 %A A067294 _Wolfdieter Lang_, Feb 05 2002