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 A105141 #8 Jun 16 2015 19:13:50
%S A105141 1,1,1,2,1,1,1,2,1,1,2,1,1,2,1,2,3,2,1,2,1,1,1,2,1,1,2,1,1,2,1,2,3,2,
%T A105141 1,2,1,1,2,1,1,2,1,2,3,2,1,2,1,1,2,1,2,3,2,1,2,1,1,2,1,2,3,2,1,2,1,2,
%U A105141 3,2,3,1,3,2,3,2,1,2,1,2,3,2,1,2,1,1,1,2,1,1,2,1,1,2,1,2,3,2,1,2,1,1,2,1,1
%N A105141 Triangle read by rows, based on the morphism f: 1->{1,2,1}, 2->{2,3,2}, 3->{3,1,3}. First row is 1. If current row is a,b,c,..., then the next row is a,b,c,...,f(a),f(b),f(c),...
%C A105141 3-symbol substitution tile called both ter dragon and fudge flake. This tile is the classic cyclotomic n=3.
%C A105141 Row n contains (3^(n+1)-1)/2 symbols.
%H A105141 F. M. Dekking, <a href="http://dx.doi.org/10.1016/0001-8708(82)90066-4">Recurrent sets</a>, Advances in Mathematics, vol. 44, no. 1 (1982), 78-104; page 96, section 4.10.
%t A105141 s[n_] := n /. {1 -> {1, 2, 1}, 2 -> {2, 3, 2}, 3 -> {3, 1, 3}}; t[a_] := Join[a, Flatten[s /@ a]]; Flatten[ NestList[t, {1}, 4]]
%Y A105141 Cf. A073058, A105202, A105203.
%K A105141 nonn,tabf
%O A105141 0,4
%A A105141 _Roger L. Bagula_, Apr 09 2005