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 A168057 #12 Jul 08 2016 20:30:23
%S A168057 1,2,12,40,80,224,576,1152,2816,6656,13312,30720,69632,139264,311296,
%T A168057 688128,1376256,3014656,6553600,13107200,28311552,60817408,121634816,
%U A168057 260046848,553648128,1107296256,2348810240,4966055936,9932111872
%N A168057 Expansion of (1+8x^2+8x^3)/((1-2x)^2*(1+2x+4x^2)).
%C A168057 Hankel transform of A168058 is (-1)^n*a(n).
%H A168057 G. C. Greubel, <a href="/A168057/b168057.txt">Table of n, a(n) for n = 0..1000</a>
%H A168057 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,8,-16).
%F A168057 a(n) = 2^n*A168056(n).
%t A168057 CoefficientList[Series[(1+8x^2+8x^3)/((1-2x)^2(1+2x+4x^2)), {x,0,50}],x] (* _Harvey P. Dale_, Mar 24 2011 *)
%t A168057 LinearRecurrence[{2, 0, 8, -16}, {1, 2, 12, 40}, 50] (* _G. C. Greubel_, Jul 08 2016 *)
%K A168057 easy,nonn
%O A168057 0,2
%A A168057 _Paul Barry_, Nov 17 2009