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 A305490 #19 Sep 05 2025 10:22:45
%S A305490 1,1,0,1,1,0,1,2,0,1,1,0,1,1,0,1,2,0,1,1,0,1,0,0,1,2,0,1,1,0,1,1,0,1,
%T A305490 2,0,1,1,0,1,1,0,1,2,0,1,1,0,1,0,0,1,2,0,1,1,0,1,1,0,1,2,0,1,1,0,1,2,
%U A305490 0,1,2,0,1,1,0,1,0,0,1,2,0,1,1,0,1,1
%N A305490 Fixed point of the morphism 0->120, 1->110, 2->100.
%C A305490 This sequence is used to generate the anti-tribonacci sequence, A265389. The positions of 1 are also the positions of 0 in Stewart's choral sequence, A116178.
%H A305490 Clark Kimberling, <a href="/A305490/b305490.txt">Table of n, a(n) for n = 1..10000</a> [a(9842) corrected by Zhuorui He, Sep 04 2025]
%e A305490 1 -> 110 -> 110110120 -> ...
%t A305490 Nest[Flatten[# /. {0 -> {1, 2, 0}, 1 -> {1, 1, 0}, 2 -> {1, 0, 0}}] &, {0}, 9];
%o A305490 (PARI) A305490(n) = {n--;while(n%9==4,n=n\9);[1,1,0,1,1,0,1,2,0][n%9+1]}; \\ _Zhuorui He_, Sep 04 2025
%Y A305490 Cf. A265389, A116178, A305495 (positions of 0), A189636 (positions of 1), A305496 (positions of 2).
%K A305490 nonn,easy,changed
%O A305490 1,8
%A A305490 _Clark Kimberling_, Jun 02 2018