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A267588
Binary representation of the middle column of the "Rule 169" elementary cellular automaton starting with a single ON (black) cell.
1
1, 10, 101, 1010, 10100, 101001, 1010011, 10100111, 101001111, 1010011111, 10100111111, 101001111111, 1010011111111, 10100111111111, 101001111111111, 1010011111111111, 10100111111111111, 101001111111111111, 1010011111111111111, 10100111111111111111
OFFSET
0,2
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
FORMULA
Conjectures from Colin Barker, Jan 18 2016 and Apr 20 2019: (Start)
a(n) = 11*a(n-1)-10*a(n-2) for n>3.
G.f.: (1-x+x^2-x^3+x^5) / ((1-x)*(1-10*x)).
(End)
MATHEMATICA
rule=169; rows=20; ca=CellularAutomaton[rule, {{1}, 0}, rows-1, {All, All}]; (* Start with single black cell *) catri=Table[Take[ca[[k]], {rows-k+1, rows+k-1}], {k, 1, rows}]; (* Truncated list of each row *) mc=Table[catri[[k]][[k]], {k, 1, rows}]; (* Keep only middle cell from each row *) Table[FromDigits[Take[mc, k]], {k, 1, rows}] (* Binary Representation of Middle Column *)
CROSSREFS
Cf. A264442.
Sequence in context: A123522 A303596 A266612 * A267514 A279809 A279749
KEYWORD
nonn,easy
AUTHOR
Robert Price, Jan 18 2016
STATUS
approved