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A170896
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Number of ON cells after n generations of the Schrandt-Ulam cellular automaton on the square grid that is described in the Comments.
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9
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0, 1, 5, 9, 13, 25, 29, 41, 53, 65, 85, 97, 117, 145, 157, 169, 181, 201, 229, 249, 285, 321, 365, 409, 445, 497, 549, 577, 605, 633, 669, 713, 757, 825, 893, 969, 1045, 1105, 1173, 1241, 1309, 1377, 1437, 1473, 1541, 1609, 1693, 1793, 1869, 1945, 2037, 2105, 2189, 2281, 2381, 2521, 2621, 2753, 2869, 2969, 3053, 3129, 3237, 3377, 3485, 3585, 3685, 3817, 3909
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OFFSET
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0,3
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COMMENTS
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The cells are the squares of the standard square grid.
Cells are either OFF or ON, once they are ON they stay ON, and we begin in generation 1 with 1 ON cell.
Each cell has 4 neighbors, those that it shares an edge with. Cells that are ON at generation n all try simultaneously to turn ON all their neighbors that are OFF. They can only do this at this point in time; afterwards they go to sleep (but stay ON).
A square Q is turned ON at generation n+1 if:
a) Q shares an edge with one and only one square P (say) that was turned ON at generation n (in which case the two squares which intersect Q only in a vertex not on that edge are called Q's "outer squares"), and
b) Q's outer squares were not turned ON in any previous generation.
c) In addition, of this set of prospective squares of the (n+1)th generation satisfying the previous condition, we eliminate all squares which are outer squares of other prospective squares.
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REFERENCES
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D. 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.
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LINKS
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FORMULA
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We do not know of a recurrence or generating function.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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