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A266444
Middle column of the "Rule 25" elementary cellular automaton starting with a single ON (black) cell.
3
1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1
OFFSET
0
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
FORMULA
Conjectures from Colin Barker, Dec 31 2015 and Apr 16 2019: (Start)
a(n) = (1-(-1)^n)/2 for n>11.
a(n) = a(n-2) for n>13.
G.f.: (1-x^2+x^4+x^9-x^10-x^11+x^13) / ((1-x)*(1+x)).
(End)
MATHEMATICA
rule=25; 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 *) Table[catri[[k]][[k]], {k, 1, rows}] (* Keep only middle cell from each row *)
CROSSREFS
Cf. A266441.
Sequence in context: A285301 A089011 A267043 * A267679 A267868 A374043
KEYWORD
nonn,easy
AUTHOR
Robert Price, Dec 29 2015
STATUS
approved