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 A332604 #15 Mar 09 2020 13:01:41
%S A332604 1,2,1,3,1,2,3,1,3,2,1,2,3,1,2,1,3,1,2,3,1,3,2,3,1,2,1,3,1,2,3,2,1,2,
%T A332604 3,1,2,1,3,1,2,3,1,3,2,1,2,3,1,2,1,3,1,2,3,2,1,2,3,1,2,1,3,2,1,2,3,1,
%U A332604 3,2,3,1,2,1,3,1,2,3,1,3,2,1,2,3,1,2,1,3
%N A332604 Limiting word over the alphabet {1,2,3} defined by the process in A332603, or, in case that process terminates, the final term in A332603.
%C A332604 Grytczuk et al. (2020) conjecture that the process in A332603 never terminates, and report that they have computed the first 5000 terms of the limiting word.
%H A332604 Jaroslaw Grytczuk, Hubert Kordulewski, Artur Niewiadomski, <a href="https://doi.org/10.37236/9264">Extremal Square-Free Words</a>, Electronic J. Combinatorics, 27 (1), 2020, #1.48.
%t A332604 sqfQ[str_] := StringFreeQ[str, x__ ~~ x__]; ext[s_] := Catch@ Block[{t}, Do[ If[sqfQ[t = StringInsert[s, e, -p]], Throw@ t], {p, StringLength[s] + 1}, {e, {"1", "2", "3"} } ]]; a[1]=1; a[n_] := a[n] = ToExpression@ ext@ ToString@ a[n-1]; IntegerDigits@ a[88] (* _Giovanni Resta_, Mar 09 2020 *)
%Y A332604 Cf. A332603.
%K A332604 nonn
%O A332604 1,2
%A A332604 _N. J. A. Sloane_, Mar 07 2020
%E A332604 More terms from _Giovanni Resta_, Mar 09 2020