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 A201967 #14 Mar 31 2020 17:23:08 %S A201967 1,2,7,20,60,178,529,1572,4671,13880,41244,122556,364173,1082134, %T A201967 3215543,9554932,28392320,84367302,250696021,744939016,2213573775, %U A201967 6577597296,19545219896,58078292664,172578671241,512814623178 %N A201967 Expansion of 1/(1-2*x-3*x^2+x^4) in powers of x. %H A201967 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,3,0,-1). %F A201967 a(n)= 2*a(n-1) + 3*a(n-2) - a(n-4), a(0)=1, a(n)=0 if n<0. %K A201967 easy,nonn %O A201967 0,2 %A A201967 _Philippe Deléham_, Dec 07 2011