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 A085297 #7 Mar 30 2012 18:36:38
%S A085297 1,1,2,2,2,2,2,2,1,1,1,2,2,2,1,1,1,1,1,1,2,2,2,2,2,2,1,1,1,1,1,1,2,2,
%T A085297 2,1,1,1,2,2,2,2,2,2,1,1,1,2,2,2,1,1,1,1,1,1,2,2,2,1,1,1,2,2,2,2,2,2,
%U A085297 1,1,1,1,1,1,2,2,2,2,2,2,1,1,1,2,2,2,1,1,1,1,1,1,2,2,2,2,2,2,1,1,1,1,1,1,2
%N A085297 Nonzero residues of Catalan sequence modulo 3; related to the Thue-Morse sequence (A001285).
%C A085297 The runs of zeros in between the digit strings are given in A085296.
%F A085297 If a leading '1' is added to the Catalan sequence modulo 3, the only nonzero digit strings are {1, 1, 1, 2, 2, 2} and {2, 2, 2, 1, 1, 1}. Replacing these digit strings with their first digit, {1, 1, 1, 2, 2, 2} -> '1' and {2, 2, 2, 1, 1, 1} -> '2', then omitting all zeros, results in the Thue-Morse sequence.
%Y A085297 Cf. A001285 (Thue-Morse), A000108 (Catalan), A039969 (d-perfect), A085296.
%K A085297 nonn
%O A085297 1,3
%A A085297 _Paul D. Hanna_, Jun 24 2003