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 A109268 #4 Dec 30 2023 16:11:54 %S A109268 1,1,4,11,36,119,407,1418,5018,17971,64989,236915,869518,3209735, %T A109268 11907644,44368636,165957615,622880402,2345005449,8852862717, %U A109268 33505203060,127096279124,483127286394,1840030664115,7020349647422 %N A109268 Expansion of 1/((1-xc(x)-x^2c(x)^2)(1-x^2c(x))) with c(x) the g.f. of A000108. %C A109268 Diagonal sums of A109267. %F A109268 G.f.: (2-x-x*sqrt(1-4x))(sqrt(1-4x)-x)/(2(1-4x-x^2)(1-x+x^3)) %K A109268 easy,nonn %O A109268 0,3 %A A109268 _Paul Barry_, Jun 24 2005