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A267258
Decimal representation of the middle column of the "Rule 111" elementary cellular automaton starting with a single ON (black) cell.
2
1, 3, 7, 15, 31, 63, 127, 255, 510, 1021, 2042, 4085, 8170, 16341, 32682, 65365, 130730, 261461, 522922, 1045845, 2091690, 4183381, 8366762, 16733525, 33467050, 66934101, 133868202, 267736405, 535472810, 1070945621, 2141891242, 4283782485, 8567564970
OFFSET
0,2
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
FORMULA
Conjectures from Colin Barker, Jan 13 2016 and Apr 17 2019: (Start)
a(n) = (383*2^n-32*((-1)^n+3))/192 for n>5.
G.f.: (1+x-x^8) / ((1-x)*(1+x)*(1-2*x)).
(End)
MATHEMATICA
rule=111; 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], 2], {k, 1, rows}] (* Binary Representation of Middle Column *)
CROSSREFS
Cf. A267253.
Sequence in context: A043747 A105754 A116690 * A305493 A213247 A043755
KEYWORD
nonn,easy
AUTHOR
Robert Price, Jan 12 2016
STATUS
approved