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 A277299 #7 Oct 11 2016 18:41:32
%S A277299 1,14,698,56410,6036632,784844330,118467338692,20204403241014,
%T A277299 3825143045741850,794096638401382028,179152196191253429864,
%U A277299 43621984527307144281094,11400895235718650585287660,3183846191638117842792003252,946381984098376099573619213864,298412976572690317096982653746772
%N A277299 Central terms of triangle A277295 in even-indexed rows; a(n) = A277295(2*n,n-1).
%C A277299 G.f. G(x,y) of triangle A277295 satisfies:
%C A277299 (1) G(x,y) = x + G( y*G(x,y) + (1-y)*x, y)^2.
%C A277299 (2) G( x - y*G(x,y)^2, y) = x + (1-y)*G(x,y)^2.
%o A277299 (PARI) {A277295(n,k) = my(A=x); for(i=1, n, A = x + subst(A^2, x, y*A + (1-y)*x +x*O(x^n)) ); polcoeff(polcoeff(A,n,x),k,y)}
%o A277299 for(n=1,20,print1(A277295(2*n,n-1),", "))
%Y A277299 Cf. A277295, A277296, A277297, A277298.
%K A277299 nonn
%O A277299 1,2
%A A277299 _Paul D. Hanna_, Oct 11 2016