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A273573
Number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 801", based on the 5-celled von Neumann neighborhood.
4
1, 4, 17, 28, 57, 84, 117, 140, 205, 264, 317, 400, 465, 512, 581, 652, 749, 928, 973, 1204, 1329, 1388, 1497, 1656, 1777, 1996, 2101, 2312, 2413, 2436, 2529, 2672, 2985, 3216, 3429, 3864, 4005, 4200, 4353, 4692, 5033, 5376, 5477, 5884, 6093, 6200, 6445
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.
MATHEMATICA
CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=801; 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}];
Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *)
CROSSREFS
Sequence in context: A335593 A319970 A272834 * A272846 A273610 A272769
KEYWORD
nonn,easy
AUTHOR
Robert Price, May 25 2016
STATUS
approved