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A216430
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(-1)^A081603(n), parity of the number of 2's in the ternary expansion of n.
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1
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1, -1, 1, 1, -1, -1, -1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, -1, -1, 1, -1, -1, 1, 1, 1, -1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, -1, -1, 1, -1, -1, 1, 1, 1, -1, -1, -1, 1, -1, -1, 1, 1, 1, -1, -1, -1, 1, -1, -1, 1, 1, 1, -1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1
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OFFSET
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1
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LINKS
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Table of n, a(n) for n=1..90.
A. Aksenov, The Newman phenomenon and Lucas sequence, arXiv:1108.5352, chapter 6.
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EXAMPLE
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a(7) = -1 because 7 is 21 (has one 2s) in base 3, and (-1)^1 = -1.
a(8) = 1 because 8 is 22 (has two 2s) in base 3, and (-1)^2 = 1.
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MAPLE
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A081603 := proc(n)
local a, d ;
a := 0 ;
for d in convert(n, base, 3) do
if d = 2 then
a := a+1 ;
end if;
end do;
a;
end proc:
A216430 := proc(n)
(-1)^A081603(n) ;
end proc:
seq(A216430(n), n=1..90) ;
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MATHEMATICA
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Table[(-1)^DigitCount[n, 3, 2], {n, 90}] (* Alonso del Arte, Sep 08 2012 *)
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CROSSREFS
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Sequence in context: A209661 A033999 A000012 * A232544 A309873 A162511
Adjacent sequences: A216427 A216428 A216429 * A216431 A216432 A216433
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KEYWORD
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sign,easy,base
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AUTHOR
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R. J. Mathar, Sep 08 2012
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STATUS
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approved
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