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A267160
Number of OFF (white) cells in the n-th iteration of the "Rule 107" elementary cellular automaton starting with a single ON (black) cell.
1
0, 2, 2, 2, 3, 3, 6, 2, 11, 4, 13, 2, 19, 4, 21, 2, 27, 4, 29, 2, 35, 4, 37, 2, 43, 4, 45, 2, 51, 4, 53, 2, 59, 4, 61, 2, 67, 4, 69, 2, 75, 4, 77, 2, 83, 4, 85, 2, 91, 4, 93, 2, 99, 4, 101, 2, 107, 4, 109, 2, 115, 4, 117, 2, 123, 4, 125, 2, 131, 4, 133, 2
OFFSET
0,2
REFERENCES
S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.
FORMULA
Conjectures from Colin Barker, Jan 11 2016 and Apr 19 2019: (Start)
a(n) = a(n-2)+a(n-4)-a(n-6) for n>11.
G.f.: x*(2+2*x+x^3-x^4+x^5-x^6+4*x^7+x^8-x^9-x^10+x^11) / ((1-x)^2*(1+x)^2*(1+x^2)).
(End)
MATHEMATICA
rule=107; 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 *) nbc=Table[Total[catri[[k]]], {k, 1, rows}]; (* Number of Black cells in stage n *) Table[Length[catri[[k]]]-nbc[[k]], {k, 1, rows}] (* Number of White cells in stage n *)
CROSSREFS
Cf. A267152.
Sequence in context: A035680 A238220 A103600 * A374436 A082861 A131704
KEYWORD
nonn,easy
AUTHOR
Robert Price, Jan 11 2016
STATUS
approved