login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1

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;

    a;

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 A162511 A157895

Adjacent sequences:  A216427 A216428 A216429 * A216431 A216432 A216433

KEYWORD

sign,easy,base

AUTHOR

R. J. Mathar, Sep 08 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 21 04:59 EDT 2019. Contains 321364 sequences. (Running on oeis4.)