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 A225188 #12 Nov 26 2020 22:26:16
%S A225188 1,2,12,21,121,212,1221,2112,122112,211221,12212112,21121221,
%T A225188 122121121221,211212212112,1221211221121221,2112122112212112,
%U A225188 122121122112122112212112,211212211221211221121221,12212112211212212112122112212112,21121221122121121221211221121221,122121122112122121121221122121121221211221121221,211212211221211212212112211212212112122112212112
%N A225188 Words u such that uu is a factor of the Thue-Morse word A001285.
%C A225188 Consists of 1, 2, 121, 212 and their repeated images under the morphism 1 -> 12, 2 -> 21.
%C A225188 These are the square roots of the words in A225186.
%C A225188 Replacing {1,2} by {0,1} gives the words u such that uu is a factor of A010060.
%H A225188 James D. Currie and Narad Rampersad, <a href="https://arxiv.org/abs/0803.1189">Infinite words containing squares at every position</a>, arXiv:0803.1189 [math.CO], 2008; or <a href="https://doi.org/10.1051/ita/2010007">also</a>, RAIRO-Theor. Inf. Appl. 44, 113-124 (2010).
%Y A225188 Cf. A001285, A020060, A225186.
%K A225188 nonn
%O A225188 1,2
%A A225188 _N. J. A. Sloane_, May 05 2013