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A273244
First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 613", based on the 5-celled von Neumann neighborhood.
1
7, 12, 25, 16, 51, 20, 69, 24, 111, 28, 96, -4, 229, -16, 188, -40, 324, -8, 208, -72, 412, -64, 384, -120, 479, -92, 385, -256, 708, -312, 763, -340, 757, -428, 976, -480, 1064, -408, 875, -532, 1104, -636, 1313, -680, 1227, -780, 1441, -880, 1751, -888
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=613; 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. A273241.
Sequence in context: A357509 A190554 A375971 * A273298 A273269 A273307
KEYWORD
sign,easy
AUTHOR
Robert Price, May 18 2016
STATUS
approved