OFFSET
-1,3
COMMENTS
We work on the square grid. A cell is turned ON iff exactly one or four of its four neighbors is ON. Once a cell is ON it stays ON. At stage -1 all cells are OFF. At stage 0 a single cell is turned ON.
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 928.
LINKS
N. J. A. Sloane, Table of n, a(n) for n = -1..549
David Applegate, The movie version
David Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191. [There is a typo in Theorem 6: (13) should read u(n) = 4.3^(wt(n-1)-1) for n >= 2.]
N. J. A. Sloane, Illustration of first 24 generations (png)
N. J. A. Sloane, Illustration of first 24 generations (pdf)
N. J. A. Sloane, Catalog of Toothpick and Cellular Automata Sequences in the OEIS
MATHEMATICA
Map[Function[Apply[Plus, Flatten[ #1]]], CellularAutomaton[{ 942, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 100]]
ArrayPlot /@ CellularAutomaton[{942, {2, {{0, 2, 0}, {2, 1, 2}, {0, 2, 0}}}, {1, 1}}, {{{1}}, 0}, 23]
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 07 2010
EXTENSIONS
Added Mma programs and illustrations. - N. J. A. Sloane, Sep 21 2014
STATUS
approved