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A160652 Express n in balanced ternary, then reverse the digits, leaving any trailing zeros alone. 1
0, 1, -2, 3, 4, -11, -6, 7, -8, 9, 10, -5, 12, 13, -38, -33, 16, -29, -18, 25, -20, 21, 34, -35, -24, 19, -26, 27, 28, -17, 30, 37, -32, -15, 22, -23, 36, 31, -14, 39, 40, -119, -114, 43, -92, -99, 70, -65, 48, 97, -110, -87, 52, -83, -54, 79, -56, 75, 106, -101 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

This sequence, together with its negative extension a(-n) = -a(n) is a self-inverse permutation of the integers. The absolute values are a self-inverse permutation of the nonnegative integers.

LINKS

Indranil Ghosh, Table of n, a(n) for n = 0..6561

FORMULA

a(n) = A134028(n)*3^A007949(n). [Franklin T. Adams-Watters, May 24 2009]

EXAMPLE

87 in balanced ternary is 101(-1)0; leaving the final 0 and reversing the remaining digits gives (-1)1010, which is -51; so a(87) = -51.

PROG

(PARI) a(n)=local(r, dr, q); if(n==0, 0, r=0; dr=1; while(n%3==0, dr*=3; n\=3); while(n!=0, q=(n+1)\3; r=3*r+dr*(n-3*q); n=q); r) \\ Franklin T. Adams-Watters, May 24 2009

(Python)

def a(n):

    if n==0: return 0

    r=0

    dr=1

    while n%3==0:

        dr*=3

        n/=3

    while n!=0:

        q=(n + 1)/3

        r=3*r + dr*(n - 3*q)

        n=q

    return r

##print [a(n) for n in xrange(101)] # Indranil Ghosh, Jun 10 2017, after Franklin T. Adams-Watters

CROSSREFS

Cf. A065363, A117962, A117966.

Cf. A057889, A134028, A007949. [Franklin T. Adams-Watters, May 24 2009]

Sequence in context: A035358 A265351 A065633 * A131485 A075833 A265904

Adjacent sequences:  A160649 A160650 A160651 * A160653 A160654 A160655

KEYWORD

base,look,sign

AUTHOR

Franklin T. Adams-Watters, May 21 2009

STATUS

approved

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Last modified January 20 23:20 EST 2019. Contains 319343 sequences. (Running on oeis4.)