A271803 Number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 401", based on the 5-celled von Neumann neighborhood.

1, 4, 5, 32, 5, 96, 17, 164, 5, 336, 25, 444, 17, 644, 61, 744, 5, 1200, 25, 1436, 25, 1724, 85, 1904, 17, 2516, 85, 2736, 61, 3176, 217, 3196, 5, 4464, 25, 4956, 25, 5500, 85, 5936, 25, 6764, 125, 7144, 85, 7856, 305, 7940, 17, 9716, 85, 10320, 85, 11024

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.

Links

Robert Price, Table of n, a(n) for n = 0..128

Robert Price, Diagrams of the first 20 stages

N. J. A. Sloane, On the Number of ON Cells in Cellular Automata, arXiv:1503.01168 [math.CO], 2015

Eric Weisstein's World of Mathematics, Elementary Cellular Automaton

S. Wolfram, A New Kind of Science

Index entries for sequences related to cellular automata

Index to 2D 5-Neighbor Cellular Automata

Index to Elementary Cellular Automata

Mathematica

CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=401; 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: A262031 A326998 A270286 * A269810 A271125 A270014

Adjacent sequences: A271800 A271801 A271802 * A271804 A271805 A271806

Keyword

nonn,easy

Author

Robert Price, Apr 14 2016

Status

approved