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 A078051 #12 Apr 07 2020 03:37:29
%S A078051 1,-2,0,3,-1,-5,4,7,-10,-8,21,5,-39,8,65,-42,-96,115,119,-253,-100,
%T A078051 487,-34,-840,421,1293,-1295,-1712,3009,1710,-6016,-413,10735,-3893,
%U A078051 -17164,14215,24006,-35272,-26955,73493,15689,-135720,30849,224902,-150880,-329773,406631,403795,-887284,-326937
%N A078051 Expansion of (1-x)/(1+x+2*x^2+x^3).
%H A078051 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (-1,-2,-1).
%t A078051 LinearRecurrence[{-1,-2,-1},{1,-2,0},50] (* _Harvey P. Dale_, Aug 18 2014 *)
%o A078051 (PARI) Vec((1-x)/(1+x+2*x^2+x^3) + O(x^50)) \\ _Jinyuan Wang_, Apr 07 2020
%Y A078051 First differences of A077979.
%K A078051 sign,easy
%O A078051 0,2
%A A078051 _N. J. A. Sloane_, Nov 17 2002