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 A078045 #14 Aug 08 2019 18:58:55
%S A078045 1,-2,1,3,-8,7,7,-30,37,7,-104,171,-53,-326,721,-501,-872,2815,-2945,
%T A078045 -1614,10189,-14465,1048,33795,-63773,32074,99289,-258909,223768,
%U A078045 233719,-975305,1189122,253621,-3393353,5517976,-1617381,-10687301,23340634,-15888095,-28827141,91396504
%N A078045 Expansion of (1-x)/(1+x+x^2-2*x^3).
%H A078045 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-1,2).
%F A078045 Recurrence: a(n) = 2a(n-3) - a(n-2) - a(n-1), starting 1,-2,1. - _Ralf Stephan_, Aug 18 2013
%t A078045 CoefficientList[Series[(1-x)/(1+x+x^2-2*x^3),{x,0,40}],x] (* or *) LinearRecurrence[{-1,-1,2},{1,-2,1},50] (* _Harvey P. Dale_, Jun 12 2016 *)
%Y A078045 First differences of A077975.
%K A078045 sign,easy
%O A078045 0,2
%A A078045 _N. J. A. Sloane_, Nov 17 2002