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 A091904 #12 Mar 08 2021 12:20:13
%S A091904 0,1,4,48,320,2816,21504,176128,1392640,11206656,89391104,716177408,
%T A091904 5725224960,45818576896,366481506304,2932120485888,23455890145280,
%U A091904 187651416129536,1501194149167104,12009621912813568,96076700424601600
%N A091904 Expansion of x/((1+4x)(1-8x)).
%C A091904 A091904(n)=A091905(n+1)/50.
%H A091904 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (4,32).
%F A091904 a(n)=8^n/12-(-4)^n/12
%F A091904 a(0)=0, a(1)=1, a(n)=4*a(n-1)+32*a(n-2). - _Harvey P. Dale_, May 06 2014
%F A091904 a(n)=4^(n-1)*A001045(n+1). - _R. J. Mathar_, Mar 08 2021
%t A091904 Join[{a=0,b=1},Table[c=4*b+32*a;a=b;b=c,{n,30}]] (* _Vladimir Joseph Stephan Orlovsky_, Apr 22 2011 *)
%t A091904 CoefficientList[Series[x/((1+4x)(1-8x)),{x,0,30}],x] (* or *) LinearRecurrence[{4,32},{0,1},30] (* _Harvey P. Dale_, May 06 2014 *)
%K A091904 easy,nonn
%O A091904 0,3
%A A091904 _Paul Barry_, Feb 10 2004