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 A049321 #31 Dec 03 2020 02:52:22
%S A049321 0,0,1,2,0,0,1,2,1,2,0,1,2,0,0,1,2,0,0,1,2,1,2,0,1,2,1,2,0,1,2,0,0,1,
%T A049321 2,1,2,0,1,2,0,0,1,2,0,0,1,2,1,2,0,1,2,0,0,1,2,0,0,1,2,1,2,0,1,2,1,2,
%U A049321 0,1,2,0,0,1,2,1,2,0,1,2,1,2,0,1,2,0,0,1,2,1,2,0,1,2,0,0,1,2,0,0,1,2,1,2,0
%N A049321 Primitive Chacon sequence: fixed under 0->0012, 1->12, 2->012.
%C A049321 This sequence was introduced by Ferenczi in his 1995 paper. It has the property that it maps to the non-primitive Chacon sequence A049320 via the letter-to-letter map 0->0, 1->1, 2->0. See Ferenczi's paper, page 281. - _Michel Dekking_, Oct 24 2019
%H A049321 Reinhard Zumkeller, <a href="/A049321/b049321.txt">Table of n, a(n) for n = 0..10000</a>
%H A049321 Scott Balchin and Dan Rust, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL20/Rust/rust3.html">Computations for Symbolic Substitutions</a>, Journal of Integer Sequences, Vol. 20 (2017), Article 17.4.1.
%H A049321 S. Ferenczi, <a href="https://doi.org/10.24033/bsmf.2260">Les transformations de Chacon: combinatoire, structure géométrique, lien avec les systèmes de complexité 2n+1</a>, Bull. Soc. Math. France 123 (1995), 271-292.
%H A049321 S. Ferenczi, <a href="http://dx.doi.org/10.1016/S0012-365X(98)00400-2">Complexity of sequences and dynamical systems</a>, Discrete Math., 206 (1999), 145-154.
%H A049321 <a href="/index/Fi#FIXEDPOINTS">Index entries for sequences that are fixed points of mappings</a>
%F A049321 a(n) = beta(0 A049320(n)), where beta is the 2-block map given by 00->0, 10->2, 01->1. - _Michel Dekking_, Oct 24 2019
%e A049321 beta(0001000...) = beta(00)beta(00)beta(01)beta(10)beta(00)beta(00)... = 001200.... - _Michel Dekking_, Oct 24 2019
%t A049321 Nest[Flatten[# /. {0 -> {0, 0, 1, 2}, 1 -> {1, 2}, 2 -> {0, 1, 2}}]&, {0}, 4] (* _Jean-François Alcover_, Oct 05 2016 *)
%o A049321 (Haskell)
%o A049321 a049321 n = a049321_list !! n
%o A049321 a049321_list = 0 : 0 : 1 : 2 : f [0,0,1,2] where
%o A049321 f xs = drop (length xs) ys ++ f ys where
%o A049321 ys = concatMap ch xs
%o A049321 ch 0 = [0,0,1,2]; ch 1 = [1,2]; ch 2 = [0,1,2]
%o A049321 -- _Reinhard Zumkeller_, Aug 14 2013
%Y A049321 Cf. A003849, A049320.
%K A049321 nonn,nice,easy
%O A049321 0,4
%A A049321 _N. J. A. Sloane_
%E A049321 More terms from Larry Reeves (larryr(AT)acm.org), Apr 12 2000