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A272455
Number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 481", based on the 5-celled von Neumann neighborhood.
4
1, 4, 13, 28, 33, 84, 69, 172, 117, 280, 153, 428, 225, 592, 281, 788, 365, 992, 445, 1228, 541, 1448, 685, 1792, 809, 2140, 857, 2388, 913, 2636, 1025, 3104, 1193, 3460, 1401, 3944, 1489, 4312, 1629, 4816, 1821, 5288, 2097, 5964, 2325, 6260, 2341, 6932
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=481; 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: A024970 A079430 A270942 * A220745 A298017 A356984
KEYWORD
nonn,easy
AUTHOR
Robert Price, Apr 29 2016
STATUS
approved