A216430 - OEIS

A216430

(-1)^A081603(n), parity of the number of 2's in the ternary expansion of n.

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

LINKS

Table of n, a(n) for n=1..90.

A. Aksenov, The Newman phenomenon and Lucas sequence, arXiv:1108.5352, chapter 6.

EXAMPLE

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.

MAPLE

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;

end proc:

A216430 := proc(n)

(-1)^A081603(n) ;

end proc:

seq(A216430(n), n=1..90) ;

MATHEMATICA

Table[(-1)^DigitCount[n, 3, 2], {n, 90}] (* Alonso del Arte, Sep 08 2012 *)

CROSSREFS

Sequence in context: A209661 A033999 A000012 * A232544 A309873 A153881

Adjacent sequences: A216427 A216428 A216429 * A216431 A216432 A216433

KEYWORD

sign,easy,base

AUTHOR

R. J. Mathar, Sep 08 2012

STATUS

approved