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 A077915 #10 Jun 13 2015 00:50:48 %S A077915 1,-1,5,-9,27,-61,159,-385,967,-2385,5935,-14705,36511,-90561,224735, %T A077915 -557569,1383487,-3432641,8517119,-21132545,52434047,-130098945, %U A077915 322800895,-800931585,1987267071,-4930795521,12234262015,-30355580929,75318094847,-186878827521,463682682879 %N A077915 Expansion of 1/((1-x)*(1+2*x-2*x^2-2*x^3)). %H A077915 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (-1,4,0,-2). %o A077915 (PARI) Vec(1/((1-x)*(1+2*x-2*x^2-2*x^3))+O(x^99)) \\ _Charles R Greathouse IV_, Sep 27 2012 %K A077915 sign,easy %O A077915 0,3 %A A077915 _N. J. A. Sloane_, Nov 17 2002