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 A020943 #13 Jul 09 2015 20:44:27
%S A020943 0,1,1,1,0,2,2,2,0,1,1,2,1,4,3,4,1,2,1,1,0,2,2,3,1,3,2,5,3,7,4,7,3,5,
%T A020943 2,3,1,3,2,2,0,1,1,2,1,4,3,5,2,4,2,4,2,5,3,7,4,8,4,10,6,11,5,11,6,10,
%U A020943 4,8,4,7,3,5,2,4,2,4,2,5,3,4,1,2,1,1,0,2,2,3,1,3,2,5,3,7,4,8,4,7,3,6,3,6,3
%N A020943 a(2n+1) = |a(2n) - a(2n-1)|, a(2n) = a(n) + a(n-1).
%C A020943 Presumably, the positions n such that a(n)=0 are the terms of A097074. - _Ivan Neretin_, Jul 06 2015
%H A020943 Ivan Neretin, <a href="/A020943/b020943.txt">Table of n, a(n) for n = 1..5461</a>
%t A020943 a = {0, 1, 1}; Do[AppendTo[a, a[[n]] + a[[n - 1]]]; AppendTo[a, Abs[a[[-1]] - a[[-2]]]], {n, 2, 51}]; a (* _Ivan Neretin_, Jul 06 2015 *)
%Y A020943 Cf. A020947, A020948, A020949, A020950.
%K A020943 nonn,look
%O A020943 1,6
%A A020943 _Clark Kimberling_
%E A020943 More terms from _Henry Bottomley_, May 16 2001