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 A103748 #8 Mar 12 2014 16:36:45
%S A103748 1,1,2,1,2,2,3,1,2,2,3,2,3,3,3,3,2,1,1,2,2,3,2,3,3,3,3,2,1,2,3,3,3,3,
%T A103748 2,1,3,3,3,2,1,3,3,2,1,3,3,2,1,3,3,2,1,3,2,1,2,2,3,2,3,3,3,3,2,1,2,3,
%U A103748 3,3,3,2,1,3,3,3,2,1,3,3,2,1,3,3,2,1,3,3,2,1,3,2,2,3,3,3,3,2,1,3,3,3,2,1,3
%N A103748 Triangle read by rows, based on the morphism f: 1->{2}, 2->{3}, 3->{3,3,2,1}. 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 A103748 Kenyon tile substitution sequence.
%H A103748 Richard Kenyon, <a href="http://arXiv.org/abs/math.MG/9505210">The Construction of Self-Similar Tilings</a>
%t A103748 s[n_] := n /. {1 -> 2, 2 -> 3, 3 -> {3, 3, 2, 1}}; t[a_] := Join[a, Flatten[s /@ a]]; Flatten[ NestList[t, {1}, 5]]
%Y A103748 Cf. A073058, A099206.
%K A103748 nonn,tabf
%O A103748 0,3
%A A103748 _Roger L. Bagula_, Mar 28 2005