A277800 Decimal representation of the x-axis, from the origin to the right edge, of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 1", based on the 5-celled von Neumann neighborhood.

1, 0, 4, 3, 16, 15, 64, 63, 256, 255, 1024, 1023, 4096, 4095, 16384, 16383, 65536, 65535, 262144, 262143, 1048576, 1048575, 4194304, 4194303, 16777216, 16777215, 67108864, 67108863, 268435456, 268435455, 1073741824, 1073741823, 4294967296, 4294967295

Offset

0,3

Comments

Initialized with a single black (ON) cell at stage zero.

Rule numbers 1, 9, 17, 25, 257, 265, 273 and 281 all generate this sequence.

References

S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.

Links

Robert Price, Table of n, a(n) for n = 0..126

Robert Price, Diagrams of 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

Formula

Conjectures from Colin Barker, Nov 01 2016: (Start)

G.f.: (1 - x^2 + 3*x^3)/((1 - x)*(1 + x)*(1 - 2*x)*(1 + 2*x)).

a(n) = 5*a(n-2) - 4*a(n-4) for n>3.

a(n) = (-2+(-2)^n+2*(-1)^n+3*2^n)/4. (End)

Mathematica

CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=1; 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}];
Table[FromDigits[Part[ca[[i]][[i]], Range[i, 2*i-1]], 2], {i, 1, stages-1}]

Crossrefs

Cf. A277797, A277798, A277799.

Sequence in context: A084471 A285122 A277773 * A278469 A280976 A285646

Adjacent sequences: A277797 A277798 A277799 * A277801 A277802 A277803

Keyword

nonn,easy

Author

Robert Price, Oct 31 2016

Status

approved