A273676 Number of active (ON,black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 833", based on the 5-celled von Neumann neighborhood.

1, 4, 33, 161, 705, 2945, 12033, 48641, 195585, 784385, 3141633, 12574721, 50315265, 201293825, 805240833, 3221094401

Offset

0,2

Comments

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

Conjecture: Rule 849 also generates this sequence. - Lars Blomberg, Jul 23 2016

Also the number of vertex cuts in the (n+1)-barbell graph for n > 1. - Eric W. Weisstein, Apr 23 2023

References

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

Links

Table of n, a(n) for n=0..15.

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, Barbell Graph

Eric Weisstein's World of Mathematics, Elementary Cellular Automaton

Eric Weisstein's World of Mathematics, Vertex Cut

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

Conjecture: a(n) = A270222(n) for n>1. - R. J. Mathar, May 30 2016

Conjecture: a(n) = 3*4^n - 4*2^n + 1, n>1. - Lars Blomberg, Jul 23 2016

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

a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n>4.

G.f.: (1 - 3*x + 19*x^2 - 22*x^3 + 8*x^4) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).

(End)

Mathematica

CAStep[rule_, a_]:=Map[rule[[10-#]]&, ListConvolve[{{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}, a, 2], {2}];
code=833; 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 *)
Part[on, 2^Range[0, Log[2, stages]]] (* Extract relevant terms *)

Crossrefs

Cf. A273675.

Sequence in context: A209034 A095671 A278671 * A013192 A273700 A273708

Adjacent sequences: A273673 A273674 A273675 * A273677 A273678 A273679

Keyword

nonn,more

Author

Robert Price, May 27 2016

Extensions

a(8)-a(15) from Lars Blomberg, Jul 23 2016

Status

approved