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.
LINKS
Eric W. Weisstein, Totalistic Cellular Automaton.
Stephen Wolfram, A New Kind of Science, page 281.
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
KEYWORD
nonn
AUTHOR
Ben Branman, Dec 25 2011
STATUS
approved