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 A308937 #42 Jul 20 2025 15:37:43 %S A308937 0,1,2,3,4,3,4,5,6,5,4,5,6,7,8,7,8,9,10,9,10,9,10,11,12,11,10,9,10,9, %T A308937 10,11,12,13,12,13,14,15,14,15,14,15,16,17,16,15,14,15,14,15,16,17,18, %U A308937 17,18,19,20,21,20,19,20,19,20,19,18,17,18,19,20,21,20 %N A308937 Langton's ant on a chair tiling: number of black cells after n moves of the ant. %C A308937 The ant begins on the inner corner of a subtile. %C A308937 On a white tile, turn 90 degrees right, flip the color of the tile, then move forward until reaching a new tile, moving as far as possible within the tile. %C A308937 On a black tile, turn 90 degrees left, then continue as above. %C A308937 The chair tiling used for this automaton is, like all aperiodic hierarchical tilings, not unique (see for example Goodman-Strauss, p. 490). See "Remarks, 2019" in links for clarification which tiling the ant lives on. %H A308937 Jinyuan Wang, <a href="/A308937/b308937.txt">Table of n, a(n) for n = 0..1000</a> %H A308937 Felix Fröhlich, <a href="/A308937/a308937.pdf">Illustration of iterations 0-50 of the ant</a>, 2019. %H A308937 Felix Fröhlich, <a href="/A308937/a308937_1.pdf">Remarks specifying the tiling used for generating the sequence</a>, 2019. %H A308937 Chaim Goodman-Strauss, <a href="https://citeseerx.ist.psu.edu/pdf/22d654a2db56e6f2d48a679a4ed9543f5ddbf703">Aperiodic Hierarchical Tilings</a>, in: J. F. Sadoc and N. Rivier, Foams and Emulsions, NATO Science Series, Series E, Vol. 354, Springer, pp 481-496, DOI:<a href="https://doi.org/10.1007/978-94-015-9157-7_28">10.1007/978-94-015-9157-7_28</a>. %H A308937 Tilings Encyclopedia, <a href="https://tilings.math.uni-bielefeld.de/substitution/chair/">Chair</a> %H A308937 Wikipedia, <a href="https://en.wikipedia.org/wiki/Langton%27s_ant">Langton's ant</a> %H A308937 <a href="/index/Rec#order_42">Index entries for linear recurrences with constant coefficients</a>, signature (0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1). %F A308937 a(n) = a(n-42) for n >= 178. - _Jinyuan Wang_, Jul 13 2025 %e A308937 See illustrations in Fröhlich, 2019. %Y A308937 Cf. A255938, A269757, A308590, A325953, A325954, A325955. %K A308937 nonn,easy %O A308937 0,3 %A A308937 _Felix Fröhlich_, Jul 01 2019 %E A308937 More terms from _Jinyuan Wang_, Jul 13 2025