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 A267889 #18 Jun 24 2025 12:53:49
%S A267889 1,110,11111,1111111,111111111,11111111111,1111111111111,
%T A267889 111111111111111,11111111111111111,1111111111111111111,
%U A267889 111111111111111111111,11111111111111111111111,1111111111111111111111111,111111111111111111111111111,11111111111111111111111111111
%N A267889 Binary representation of the n-th iteration of the "Rule 239" elementary cellular automaton starting with a single ON (black) cell.
%C A267889 Seems to differ from A267887 and A100706 only at a(1). - _R. J. Mathar_, Jun 24 2025
%D A267889 S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
%H A267889 Robert Price, <a href="/A267889/b267889.txt">Table of n, a(n) for n = 0..1000</a>
%H A267889 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A267889 S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H A267889 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A267889 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%F A267889 Conjectures from _Colin Barker_, Jan 22 2016 and Apr 17 2019: (Start)
%F A267889 a(n) = 101*a(n-1)-100*a(n-2) for n>3.
%F A267889 G.f.: (1+9*x+101*x^2-100*x^3) / ((1-x)*(1-100*x)).
%F A267889 (End)
%t A267889 rule=239; rows=20; ca=CellularAutomaton[rule,{{1},0},rows-1,{All,All}]; (* Start with single black cell *) catri=Table[Take[ca[[k]],{rows-k+1,rows+k-1}],{k,1,rows}]; (* Truncated list of each row *) Table[FromDigits[catri[[k]]],{k,1,rows}] (* Binary Representation of Rows *)
%Y A267889 Cf. A267871.
%K A267889 nonn,easy
%O A267889 0,2
%A A267889 _Robert Price_, Jan 21 2016