cp's OEIS Frontend

A266217 Binary representation of the n-th iteration of the "Rule 7" elementary cellular automaton starting with a single ON (black) cell.

%I A266217 #26 Feb 16 2025 08:33:28
%S A266217 1,110,0,1111111,0,11111111111,0,111111111111111,0,
%T A266217 1111111111111111111,0,11111111111111111111111,0,
%U A266217 111111111111111111111111111,0,1111111111111111111111111111111,0,11111111111111111111111111111111111,0,111111111111111111111111111111111111111
%N A266217 Binary representation of the n-th iteration of the "Rule 7" elementary cellular automaton starting with a single ON (black) cell.
%H A266217 Robert Price, <a href="/A266217/b266217.txt">Table of n, a(n) for n = 0..499</a>
%H A266217 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H A266217 Stephen Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>, Wolfram Media, 2002; p. 55.
%H A266217 <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H A266217 <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%H A266217 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,10001,0,-10000).
%F A266217 From _Colin Barker_, Dec 25 2015 and Apr 13 2019: (Start)
%F A266217 a(n) = 10001*a(n-2) - 10000*a(n-4) for n>5.
%F A266217 G.f.: (1 + 110*x - 10001*x^2 + 11001*x^3 + 10000*x^4 - 10000*x^5) / ((1-x)*(1+x)*(1-100*x)*(1+100*x)).
%F A266217 (End)
%F A266217 a(n) = ((10*100^n - 1)/9)*(n mod 2) + 0^n - 0^abs(n-1). - _Karl V. Keller, Jr._, Aug 26 2021
%t A266217 rule=7; 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 *)
%o A266217 (Python) print([(10*100**n - 1)//9*(n%2) + 0**n - 0**abs(n-1) for n in range(50)]) # _Karl V. Keller, Jr._, Aug 26 2021
%Y A266217 Cf. A266216, A266218.
%K A266217 nonn,easy
%O A266217 0,2
%A A266217 _Robert Price_, Dec 24 2015