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 A077886 #9 Oct 03 2016 11:33:52
%S A077886 1,1,1,-1,-1,-1,3,3,3,-5,-5,-5,11,11,11,-21,-21,-21,43,43,43,-85,-85,
%T A077886 -85,171,171,171,-341,-341,-341,683,683,683,-1365,-1365,-1365,2731,
%U A077886 2731,2731,-5461,-5461,-5461,10923,10923,10923,-21845,-21845,-21845,43691,43691,43691,-87381,-87381,-87381,174763
%N A077886 Expansion of (1-x)^(-1)/(1+2*x^3).
%H A077886 Harvey P. Dale, <a href="/A077886/b077886.txt">Table of n, a(n) for n = 0..1000</a>
%H A077886 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,-2,2).
%F A077886 a(0)=1, a(1)=1, a(2)=1, a(3)=-1, a(n)=a(n-1)-2*a(n-3)+2*a (n-4). - _Harvey P. Dale_, Apr 30 2016
%t A077886 CoefficientList[Series[(1-x)^(-1)/(1+2x^3),{x,0,60}],x] (* or *) LinearRecurrence[{1,0,-2,2},{1,1,1,-1},60] (* _Harvey P. Dale_, Apr 30 2016 *)
%o A077886 (PARI) a(n)=([0,1,0,0; 0,0,1,0; 0,0,0,1; 2,-2,0,1]^n*[1;1;1;-1])[1,1] \\ _Charles R Greathouse IV_, Oct 03 2016
%K A077886 sign,easy
%O A077886 0,7
%A A077886 _N. J. A. Sloane_, Nov 17 2002