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 A077901 #11 May 29 2018 13:57:00
%S A077901 1,0,2,1,2,4,1,8,2,9,10,4,25,0,34,17,18,68,-15,120,2,89,154,-60,393,
%T A077901 -144,418,225,-94,1156,-799,1768,-254,425,2858,-2940,6649,-3872,4642,
%U A077901 4785,-7886,21956,-20271,26456,-2814,-11271,61370,-78268,117097,-72624,33186,128385,-240446,435204
%N A077901 Expansion of (1-x)^(-1)/(1+x-x^2-2*x^3).
%H A077901 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,1,-2).
%t A077901 CoefficientList[Series[(1-x)^(-1)/(1+x-x^2-2x^3),{x,0,80}],x] (* _Harvey P. Dale_, Mar 20 2011 *)
%o A077901 (PARI) Vec((1-x)^(-1)/(1+x-x^2-2*x^3)+O(x^99)) \\ _Charles R Greathouse IV_, Sep 27 2012
%Y A077901 First differences are in A077971.
%K A077901 sign,easy
%O A077901 0,3
%A A077901 _N. J. A. Sloane_, Nov 17 2002