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 A077926 #12 Jun 08 2020 10:44:43 %S A077926 1,-1,3,-6,14,-30,67,-147,325,-716,1580,-3484,7685,-16949,37383, %T A077926 -82450,181850,-401082,884615,-1951079,4303241,-9491096,20933272, %U A077926 -46169784,101830665,-224594601,495358987,-1092548638,2409691878,-5314742742,11722034123,-25853760123,57022262989,-125766560100 %N A077926 Expansion of (1-x)^(-1)/(1+2*x+x^3). %H A077926 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (-1,2,-1,1). %F A077926 a(n)=-a(n-1)+2*a(n-2)-a(n-3)+a(n-4). - _N-E. Fahssi_, Mar 29 2008 %F A077926 a(n) -a(n-1) = (-1)^n*A008998(n). - _R. J. Mathar_, Jun 08 2020 %o A077926 (PARI) Vec((1-x)^(-1)/(1+2*x+x^3)+O(x^99)) \\ _Charles R Greathouse IV_, Sep 27 2012 %K A077926 sign,easy %O A077926 0,3 %A A077926 _N. J. A. Sloane_, Nov 17 2002