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 A104105 #11 Oct 13 2019 10:17:53
%S A104105 1,0,0,1,0,1,1,1,0,1,1,0,1,0,0,0,0,1,1,0,1,0,0,0,1,0,0,1,0,1,1,1,0,1,
%T A104105 1,0,1,0,0,0,1,0,0,1,0,1,1,1,1,0,0,1,0,1,1,1,0,1,1,0,1,0,0,0,0,1,1,0,
%U A104105 1,0,0,0,1,0,0,1,0,1,1,1,1,0,0,1,0,1,1,1,0,1,1,0,1,0,0,0,1,0,0,1,0,1,1,1,0
%N A104105 a(1) = 1, if A(k) = sequence of first 2^k -1 terms and if B(k) is A(k) with 0's and 1's exchanged, then A(k+1) = A(k),1,B(k) if a(k) = 0, A(k+1) = A(k),0,B(k) if a(k) = 1.
%t A104105 f[l_]:=Join[l,1-{l[[Log[2,Length[l]+1]]]},1-l];Nest[f,{1},7] (* _Ray Chandler_, Apr 05 2009 *)
%Y A104105 Cf. A104104, A104106, A104107, A104108.
%K A104105 easy,nonn
%O A104105 1,1
%A A104105 _Leroy Quet_, Mar 04 2005
%E A104105 Edited and extended by _Ray Chandler_, Apr 05 2009