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A272450
First differences of number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 475", based on the 5-celled von Neumann neighborhood.
1
4, 4, 23, -3, 55, -23, 111, -87, 199, -143, 247, -195, 383, -295, 423, -351, 651, -631, 871, -751, 951, -799, 1091, -919, 1231, -1107, 1431, -1359, 1675, -1431, 1887, -1683, 2215, -2423, 2855, -2483, 2923, -2831, 3351, -3015, 3455, -3287, 4127, -4043, 4603
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=475; 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. A272447.
Sequence in context: A072696 A075219 A264650 * A271892 A271538 A271457
KEYWORD
sign,easy
AUTHOR
Robert Price, Apr 29 2016
STATUS
approved