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 A168494 #13 Sep 08 2013 13:31:50
%S A168494 1,1,2,7,32,160,830,4405,23798,130498,724748,4069258,23064608,
%T A168494 131809108,758696492,4394825647,25600773272,149877922228,881394158558,
%U A168494 5204245242208,30841413359186,183381577399006,1093695670905206
%N A168494 Sequence with Hankel transform equal to 3^floor(n^2/3).
%C A168494 Hankel transform is A168495.
%H A168494 Vincenzo Librandi, <a href="/A168494/b168494.txt">Table of n, a(n) for n = 0..300</a>
%F A168494 G.f.: 1/(1-x/(1-x/(1-3x/(1-x/(1-x/(1-3x/(1-x/(1-x/(1-3x/(1-.... (continued fraction);
%F A168494 G.f.: 1/(1-x-x^2/(1-4x-3x^2/(1-2x-3x^2/(1-4x-x^2/(1-4x-3x^2/(1-2x-3x^2/(1-4x-x^2/(1-... (continued fraction),
%F A168494 with sequences (1,3,3,1,3,3,1,3,3,1,...) and (1,4,2,4,4,2,4,4,2,4,4,...).
%F A168494 G.f.: (1+x-sqrt(1-10x+25x^2-12x^3))/(6x(1-x)).
%F A168494 a(n) = Sum_{k=0..n} A091866(n,k)*3^(n-k). - _Philippe Deléham_, Nov 27 2009
%F A168494 Conjecture: (n+1)*a(n) +(4-11*n)*a(n-2) +5*(7*n-11)*a(n-2) +(92-37*n) * a(n-3) +6*(2*n-7)*a(n-4) = 0. - _R. J. Mathar_, Sep 30 2012
%F A168494 a(n) ~ sqrt(33-sqrt(33))*((7+sqrt(33))/2)^n/(12*sqrt(Pi)*n^(3/2)). - _Vaclav Kotesovec_, Oct 24 2012
%t A168494 CoefficientList[Series[(1+x-Sqrt[1-10*x+25*x^2-12*x^3])/(6*x*(1-x)), {x, 0, 20}], x] (* _Vaclav Kotesovec_, Oct 24 2012 *)
%Y A168494 Cf. A000108, A091866, A109033. - _Philippe Deléham_, Nov 27 2009
%K A168494 easy,nonn
%O A168494 0,3
%A A168494 _Paul Barry_, Nov 27 2009