%I #20 Apr 08 2017 18:17:48
%S 1,0,1,1,0,0,0,1,1,0,0,0,0,0,1,1,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,
%T 1,1,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,
%U 0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0
%N Triangle read by rows giving successive states of cellular automaton generated by "Rule 84" initiated with a single ON (black) cell.
%C Row n has length 2n+1.
%C This sequence is also generated by Rules 116, 212 and 244.
%D S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
%H Robert Price, <a href="/A267006/b267006.txt">Table of n, a(n) for n = 0..10000</a>
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/ElementaryCellularAutomaton.html">Elementary Cellular Automaton</a>
%H S. Wolfram, <a href="http://wolframscience.com/">A New Kind of Science</a>
%H <a href="/index/Ce#cell">Index entries for sequences related to cellular automata</a>
%H <a href="https://oeis.org/wiki/Index_to_Elementary_Cellular_Automata">Index to Elementary Cellular Automata</a>
%e The first ten rows:
%e 1
%e 0 1 1
%e 0 0 0 1 1
%e 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1
%e 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1
%p seq(abs( floor(sqrt(n+2)) - 2*floor(sqrt(n+1)) + floor(sqrt(n)) ), n = 0..100); # _Peter Bala_, Apr 08 2017
%t rule=84; 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 *) Flatten[catri] (* Triangle Representation of CA *)
%o (PARI) for(n=0, 100, print1(abs(sqrtint(n + 2) - 2*sqrtint(n + 1) + sqrtint(n)),", ")) \\ _Indranil Ghosh_, Apr 08 2017
%Y Cf. A266298.
%K nonn,tabf,easy
%O 0
%A _Robert Price_, Jan 08 2016
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