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A202857
Value of the one-dimensional radius 2 totalistic 2-color cellular automaton rule 20 after 1 step, with initial condition n.
0
0, 0, 15, 0, 7, 15, 17, 0, 3, 7, 19, 15, 25, 17, 45, 0, 1, 3, 23, 7, 27, 19, 41, 15, 29, 25, 107, 17, 37, 45, 85, 0, 0, 1, 31, 3, 31, 23, 33, 7, 31, 27, 99, 19, 33, 41, 93, 15, 31, 29, 231, 25, 99, 107, 217, 17, 33, 37, 155, 45, 93, 85, 165, 0, 0, 0, 15, 1
OFFSET
1,3
COMMENTS
The initial pattern is the binary representation of n. A cell becomes live in the next step if either 2 or 4 of its neighbors (including itself) was live in the previous step. The output is interpreted as a binary integer, with factors of 2 removed.
FORMULA
a(2n) = a(n).
EXAMPLE
For n=3, the system's evolution for 1 step is:
001100 = 3,
011110 = 15.
MATHEMATICA
input[x_] := RealDigits[x, 2]; step[x_] := Flatten[CellularAutomaton[{20, {2, 1}, 2}, {Part[input[x], 1], 0}, {{1}}]]; a[x_] := FromDigits[step[x], 2]; Table[a[n], {n, 100}]
CROSSREFS
Sequence in context: A271763 A362267 A271339 * A055965 A067154 A187486
KEYWORD
nonn
AUTHOR
Ben Branman, Dec 25 2011
STATUS
approved