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 A077900 #7 Feb 28 2019 04:51:11 %S A077900 1,0,3,-4,11,-24,55,-124,283,-640,1455,-3300,7491,-17000,38583,-87564, %T A077900 198731,-451024,1023615,-2323124,5272403,-11965880,27156935,-61633500, %U A077900 139879131,-317460000,720485263,-1635163524,3711054051,-8422351624,19114786775,-43381598124,98455874923 %N A077900 Expansion of (1-x)^(-1)/(1+x-2*x^2+2*x^3). %H A077900 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,3,-4,2). %F A077900 A077970(n) = a(n)-a(n-1). - _R. J. Mathar_, Feb 28 2019 %K A077900 sign,easy %O A077900 0,3 %A A077900 _N. J. A. Sloane_, Nov 17 2002