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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
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 range(101)] # Indranil Ghosh, Jun 10 2017, after Franklin T. Adams-Watters
CROSSREFS
Sequence in context: A035358 A265351 A065633 * A131485 A325692 A075833
KEYWORD
base,look,sign
AUTHOR
STATUS
approved

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Last modified April 22 01:34 EDT 2024. Contains 371887 sequences. (Running on oeis4.)