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 A049601 #11 Oct 26 2015 07:47:42
%S A049601 0,0,2,3,12,25,76,182,504,1275,3410,8811,23256,60580,159094,415715,
%T A049601 1089648,2850645,7466468,19541994,51170460,133951675,350713222,
%U A049601 918141623,2403786672,6293097000,16475700746,43133687427,112925875764
%N A049601 a(n)=Sum{T(2i,n-2i): i=0,1,...,[ n/2 ]}, array T as in A049600.
%H A049601 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,3,-4,1).
%F A049601 G.f.: x^2*(-2+x) / ( (x^2-x-1)*(x^2-3*x+1) ).
%F A049601 a(n) = (Fibonacci(2*n)+(-1)^n*Fibonacci(n))/2. - _Vladeta Jovovic_, Aug 30 2004
%Y A049601 Cf. A049602.
%K A049601 nonn,easy
%O A049601 0,3
%A A049601 _Clark Kimberling_