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A270682
Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 190", based on the 5-celled von Neumann neighborhood.
0
1, 5, 24, 88, 312, 1144, 4344, 16888, 66552, 264184, 1052664, 4202488, 16793592, 67141624, 268500984, 1073872888
OFFSET
0,2
COMMENTS
Initialized with a single black (ON) cell at stage zero.
Conjecture: Rule 254 also generates this sequence. - Lars Blomberg, Jun 03 2016
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 170.
FORMULA
Conjecture: a(n) = 4^n + 4*2^n - 8, n>1. - Lars Blomberg, Jun 03 2016
Conjectures from Colin Barker, Jun 08 2016: (Start)
a(n) = 7*a(n-1)-14*a(n-2)+8*a(n-3) for n>4.
G.f.: (1-2*x+3*x^2-18*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=190; 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. A270681.
Sequence in context: A270906 A268587 A334459 * A272420 A089095 A220316
KEYWORD
nonn,more
AUTHOR
Robert Price, Mar 21 2016
EXTENSIONS
a(8)-a(15) from Lars Blomberg, Jun 03 2016
STATUS
approved