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 A086889 #5 Mar 30 2012 18:39:21 %S A086889 0,0,0,0,-1,1,-3,-3,-41,140,-93456,280356252,-471833669834248, %T A086889 40261350925439315783335171, %U A086889 20143180524957577201436416071451979623101429,9048277144756224572757714728840507662214586396123974675011643142128755383165 %N A086889 Real part of Propp's cubic recurrence starting with i (i^2=-1). %C A086889 b(n)=x(n)+i*y(n) where x(n) and y(n) are integer sequences. %F A086889 a(n)=Re(b(n)) where b(1)=b(2)=b(3)=b(4)=i and b(n)=(1+b(n-1)*b(n-2)*b(n-3))/b(n-4) %Y A086889 Cf. A051786, A086890. %K A086889 sign %O A086889 1,7 %A A086889 _Benoit Cloitre_, Sep 17 2003