A327252 Balanced reversed ternary: Write n as ternary, reverse the order of the digits, then replace all 2's with (-1)'s.

0, 1, -1, 1, 4, -2, -1, 2, -4, 1, 10, -8, 4, 13, -5, -2, 7, -11, -1, 8, -10, 2, 11, -7, -4, 5, -13, 1, 28, -26, 10, 37, -17, -8, 19, -35, 4, 31, -23, 13, 40, -14, -5, 22, -32, -2, 25, -29, 7, 34, -20, -11, 16, -38, -1, 26, -28, 8, 35, -19, -10, 17, -37, 2, 29, -25, 11

Offset

0,5

Links

Rémy Sigrist, Table of n, a(n) for n = 0..19683

Example

5 in base 3 is 12; reversing the ternary gives 21; replacing the 2 with (-1) gives (-1),1 which is -2 in decimal.

Maple

a:= proc(n) local m, r; m, r:= n, 0;
      while m>0 do m, r:= iquo(m, 3), 3*r+mods(m, 3) od; r
    end:
seq(a(n), n=0..3^4-1);  # Alois P. Heinz, Sep 17 2019

Mathematica

a[n_] := FromDigits[Reverse[IntegerDigits[n, 3]] /. {2 -> -1}, 3]; Array[a, 67, 0] (* Giovanni Resta, Sep 17 2019 *)

Prog

(Python)
def a(n):
    ternary = []
    i = math.floor(math.log(n, 3))
    while i >= 0:
        for j in range (2, -1, -1):
            if j*(3**i) <= n:
                if (j==2): ternary.append(-1)
                else: ternary.append(j)
                n -= j*(3**i)
                break
        i -=1
    for k in range (0, len(ternary)):
        n += ternary[k]*(3**k)
    return n
(PARI) a(n) = fromdigits(apply(d -> if (d==2, -1, d), Vecrev(digits(n, 3))), 3) \\ Rémy Sigrist, Sep 15 2019

Crossrefs

Cf. A134028 (reversed balanced ternary, i.e. balancing the ternary, then reversing the ternary and transforming back into decimal), A117966 (balanced ternary enumeration).

Sequence in context: A016507 A270047 A132116 * A229974 A364789 A281065

Adjacent sequences: A327249 A327250 A327251 * A327253 A327254 A327255

Keyword

sign,look,base

Author

Elisabeth Zemack, Sep 15 2019

Status

approved