

A151725


Number of ON states after n generations of cellular automaton based on square grid with each cell adjacent to its eight neighbors.


13



0, 1, 9, 13, 33, 37, 57, 77, 121, 125, 145, 165, 209, 237, 297, 373, 465, 469, 489, 509, 553, 581, 641, 717, 809, 837, 897, 981, 1097, 1213, 1409, 1645, 1833, 1837, 1857, 1877, 1921, 1949, 2009, 2085, 2177, 2205, 2265, 2349, 2465, 2581, 2777, 3013
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OFFSET

0,3


COMMENTS

A cell is turned ON if exactly one of its eight neighbors is ON. An ON cell remains ON for ever.
We start with a single ON cell.
Analog of A147562, which is the case when each cell has only four neighbors.
The equivalent Mathematica cellular automaton is obtained with neighborhood weights {{1,1,1},{1,9,1},{1,1,1}}, rule number 261634, and starting configuration {{1}}. [From John W. Layman, Sep 11 2009]
Observation: Visual pattern similar to the toothpick structure (see A139250). [From Omar E. Pol, Dec 14 2009]


REFERENCES

N. H. Packard and S. Wolfram, TwoDimensional Cellular Automata, Journal of Statistical Physics, 38 (1985), 901946. [From Omar E. Pol, Apr 08 2010] (See Fig. 7e.)


LINKS

David Applegate, Table of n, a(n) for n = 0..1000
David Applegate, The movie version
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata
N. H. Packard and S. Wolfram, TwoDimensional Cellular Automata, Journal of Statistical Physics, 38 (1985), 901946. (See page 920, Figure 7e). [From Omar E. Pol, Apr 08 2010]
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS


FORMULA

For a recurrence see the ApplegatePolSloane paper.


MATHEMATICA

RasterGraphics[state_?MatrixQ, colors_Integer : 2, opts___] := Graphics[Raster[ Reverse[1  state/(colors  1)]], AspectRatio > (AspectRatio /. {opts} /. AspectRatio > Automatic), Frame > True, FrameTicks > None, GridLines > None]; wt = {{1, 1, 1}, {1, 9, 1}, {1, 1, 1}}; rule= 261634; init={{1}}; Show[GraphicsArray[Map[RasterGraphics, CellularAutomaton[{rule, {2, wt}, {1, 1}}, {init, 0}, 9, 10]]]]; nx = 100; ca = CellularAutomaton[{rule, {2, wt}, {1, 1}}, {init, 0}, nx  1, nx]; a = Table[Total[ca[[i]], 2], {i, 1, nx}] [From John W. Layman, Sep 11 2009]


CROSSREFS

Cf. A139250, A151726, A147562, A147582, A151723, A151735, A151747, A151728.
See A151731, A151732, A151733, A151734 for the same CA except that two neighbors must be ON for a cell to turn ON.
Sequence in context: A098074 A032361 A031196 * A146864 A146739 A146723
Adjacent sequences: A151722 A151723 A151724 * A151726 A151727 A151728


KEYWORD

nonn,changed


AUTHOR

David Applegate and N. J. A. Sloane, Jun 13 2009


STATUS

approved



