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A270130 Number of active (ON,black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 89", based on the 5-celled von Neumann neighborhood. 0
1, 4, 44, 225, 961, 3969, 16129, 65025, 261121, 1046529, 4190209, 16769025, 67092481, 268402689, 1073676289, 4294836225 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Initialized with a single black (ON) cell at stage zero.
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
LINKS
N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168 [math.CO], 2015
Eric Weisstein's World of Mathematics, Elementary Cellular Automaton
FORMULA
Conjecture: a(n) = 4*4^n - 4*2^n + 1, n>2. - Lars Blomberg, Apr 23 2016
Conjectures from Colin Barker, Jun 08 2016: (Start)
a(n) = 7*a(n-1)-14*a(n-2)+8*a(n-3) for n>5.
G.f.: (1-3*x+30*x^2-35*x^3-30*x^4+40*x^5) / ((1-x)*(1-2*x)*(1-4*x)).
(End)
MATHEMATICA
CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=89; stages=128;
rule=IntegerDigits[code, 2, 10];
g=2*stages+1; (* Maximum size of grid *)
a=PadLeft[{{1}}, {g, g}, 0, Floor[{g, g}/2]]; (* Initial ON cell on grid *)
ca=a;
ca=Table[ca=CAStep[rule, ca], {n, 1, stages+1}];
PrependTo[ca, a];
(* Trim full grid to reflect growth by one cell at each stage *)
k=(Length[ca[[1]]]+1)/2;
ca=Table[Table[Part[ca[[n]][[j]], Range[k+1-n, k-1+n]], {j, k+1-n, k-1+n}], {n, 1, k}];
on=Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *)
Part[on, 2^Range[0, Log[2, stages]]] (* Extract relevant terms *)
CROSSREFS
Cf. A270129.
Sequence in context: A077435 A271294 A269907 * A074751 A129551 A202162
KEYWORD
nonn,more
AUTHOR
Robert Price, Mar 11 2016
EXTENSIONS
a(8)-a(15) from Lars Blomberg, Apr 23 2016
STATUS
approved

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Last modified July 12 17:26 EDT 2024. Contains 374251 sequences. (Running on oeis4.)