

A272737


First differences of number of active (ON,black) cells in nth stage of growth of twodimensional cellular automaton defined by "Rule 521", based on the 5celled von Neumann neighborhood.


1



3, 9, 11, 29, 16, 36, 11, 97, 7, 69, 7, 137, 15, 81, 39, 237, 25, 133, 17, 281, 17, 145, 35, 377, 97, 277, 41, 309, 103, 73, 159, 465, 109, 269, 57, 537, 41, 249, 19, 721, 249, 501, 49, 509, 119, 33, 411, 621, 293, 537, 177, 877, 57, 161, 339
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OFFSET

0,1


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..127
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 5Neighbor 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=521; 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+1n, k1+n]], {j, k+1n, k1+n}], {n, 1, k}];
on=Map[Function[Apply[Plus, Flatten[#1]]], ca] (* Count ON cells at each stage *)
Table[on[[i+1]]on[[i]], {i, 1, Length[on]1}] (* Difference at each stage *)


CROSSREFS

Cf. A272734.
Sequence in context: A018381 A227969 A272704 * A273533 A268033 A145812
Adjacent sequences: A272734 A272735 A272736 * A272738 A272739 A272740


KEYWORD

sign,easy


AUTHOR

Robert Price, May 05 2016


STATUS

approved



