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A272559
First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 497", based on the 5-celled von Neumann neighborhood.
1
3, 9, 23, 1, 51, -3, 71, -47, 159, -87, 199, -143, 327, -199, 375, -423, 711, -635, 967, -967, 1107, -719, 819, -739, 1199, -1067, 1423, -1315, 1699, -1331, 1571, -1599, 2391, -2487, 3043, -2871, 3223, -2859, 3195, -3039, 3655, -3395, 3955, -3619, 4071
OFFSET
0,1
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=497; 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 *)
Table[on[[i+1]]-on[[i]], {i, 1, Length[on]-1}] (* Difference at each stage *)
CROSSREFS
Cf. A272556.
Sequence in context: A197666 A146009 A326007 * A270991 A029512 A210027
KEYWORD
sign,easy
AUTHOR
Robert Price, May 02 2016
STATUS
approved