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 A214217 #17 Aug 06 2024 10:36:46
%S A214217 2,11,212,11211,21211212,1121121211211,212112121121121211212,
%T A214217 1121121211211212112121121121211211,
%U A214217 2121121211211212112121121121211211212112121121121211212,11211212112112121121211211212112112121121211211212112121121121211211212112121121121211211
%N A214217 List of singular subwords (or factors) of the Fibonacci word A003842.
%C A214217 Complementing the first and last digits of each term gives (essentially) A214216.
%H A214217 Kalle Saari, <a href="https://citeseerx.ist.psu.edu/pdf/226ad5ee4e916bbddb5775d36d4d126074ca1c27">Periods of factors of the Fibonacci word</a>, Department of Mathematics and Turku Centre for Computer Science, University of Turku, 2001 4 Turku, Finland.
%H A214217 Kalle Saari, <a href="https://www.semanticscholar.org/paper/PERIODS-OF-FACTORS-OF-THE-FIBONACCI-WORD-KALLE-Saari/226ad5ee4e916bbddb5775d36d4d126074ca1c27">Periods of factors of the Fibonacci word</a>, in Proceedings of the Sixth International Conference on Words (WORDS’07). Institut de Mathématiques de Luminy (2007) 273-279.
%H A214217 Zhi-Xiong Wen and Zhi-Ying Wen, <a href="https://doi.org/10.1006/eujc.1994.1060">Some properties of the singular words of the Fibonacci word</a>, European J. Combin. 15 (1994), 587-598.
%F A214217 a(0)=2, a(1)=11, a(2)=212; thereafter a(n)=the concatenation of a(n-2), a(n-3), and a(n-2). [clarified by _Harvey P. Dale_, May 24 2018]
%t A214217 nxt[{a_,b_,c_}]:={b,c,FromDigits[Join[Flatten[IntegerDigits/@{b,a,b}]]]}; NestList[nxt,{2,11,212},10][[All,1]] (* _Harvey P. Dale_, May 24 2018 *)
%Y A214217 Cf. A003842, A214216.
%K A214217 nonn
%O A214217 1,1
%A A214217 _N. J. A. Sloane_, Jul 10 2012