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 A080814 #11 Dec 24 2023 17:00:04
%S A080814 1,12,1221,12212112,1221211221121221,12212112211212212112122112212112,
%T A080814 1221211221121221211212211221211221121221122121121221211221121221
%N A080814 Successive words in the formal D0L language that produces the Thue-Morse sequence A001285 (start with 1, map 1 -> 12, 2 -> 21).
%D A080814 A. Salomaa, Jewels of Formal Language Theory. Computer Science Press, Rockville, MD, 1981, p. 5.
%H A080814 Jarosław Grytczuk, <a href="http://dx.doi.org/10.1016/j.disc.2007.08.039">Thue type problems for graphs, points and numbers</a>, Discrete Math., 308 (2008), 4419-4429.
%t A080814 Map[FromDigits,SubstitutionSystem[{1->{1,2},2->{2,1}},{1},7]] (* _Paolo Xausa_, Dec 24 2023 *)
%Y A080814 Cf. A001285 (which is the limiting word), A010060, A080815.
%K A080814 nonn
%O A080814 1,2
%A A080814 _N. J. A. Sloane_, Mar 26 2003