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A271159
First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 302", based on the 5-celled von Neumann neighborhood.
1
4, 3, 13, 3, 13, 7, 41, 11, -11, 15, 65, -45, 60, 25, 115, 52, -115, 51, 128, -160, 72, 44, 132, 4, -28, 52, 136, -112, 184, 88, 320, 184, -420, 132, 372, -676, 376, 72, 72, -60, 16, 8, 168, -52, 44, 76, 412, 36, -232, 24, 504, -608, 356, 52, 452, -44, -116
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=302; 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. A271156.
Sequence in context: A271284 A272312 A272117 * A268276 A169706 A355933
KEYWORD
sign,easy
AUTHOR
Robert Price, Mar 31 2016
STATUS
approved