A270018 Number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 51", based on the 5-celled von Neumann neighborhood.

1, 5, 5, 37, 9, 109, 13, 213, 13, 333, 29, 493, 33, 685, 69, 877, 77, 1133, 93, 1421, 85, 1725, 125, 2069, 137, 2457, 141, 2837, 165, 3293, 181, 3757, 209, 4209, 233, 4733, 289, 5285, 309, 5837, 309, 6481, 405, 7173, 325, 7789, 413, 8525, 457, 9237, 421

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=51; 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: A270325 A270930 A269814 * A269876 A139386 A074947

Adjacent sequences: A270015 A270016 A270017 * A270019 A270020 A270021

Keyword

nonn,easy

Author

Robert Price, Mar 08 2016

Status

approved