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 A143848 #12 Jul 11 2024 21:44:26 %S A143848 1,1,0,-9,80,6111,29951360,-207256402585089, %T A143848 -3919788933040280447085605363200, %U A143848 14683863149476410414382246646213355893861151824423487368369151 %N A143848 Let x(1) = 1 and x(n) = x(n-1)^2 + i for n>1; a(n) is the real part of x(n). %F A143848 a(n+1) = a(n)^2 - A143849(n)^2. %e A143848 The x(n) sequence starts 1, 1+i, 3*i, -9+i, 80-17*i, 6111-2719*i, ... %Y A143848 A143849 gives the imaginary part of x(n). %K A143848 sign %O A143848 1,4 %A A143848 _Reinhard Zumkeller_, Sep 03 2008 %E A143848 Definition clarified by _N. J. A. Sloane_, Jul 11 2024 at the suggestion of _Harvey P. Dale_.