A338828 For any number with ternary representation (t(1), t(2), ..., t(k)), the ternary representation of a(n) is (abs(t(1)-t(k)), abs(t(2)-t(k-1)), ..., abs(t(k)-t(1))).

0, 0, 0, 4, 0, 4, 8, 4, 0, 10, 0, 10, 10, 0, 10, 10, 0, 10, 20, 10, 0, 20, 10, 0, 20, 10, 0, 28, 0, 28, 40, 12, 40, 52, 24, 52, 40, 12, 40, 28, 0, 28, 40, 12, 40, 52, 24, 52, 40, 12, 40, 28, 0, 28, 56, 28, 0, 68, 40, 12, 80, 52, 24, 68, 40, 12, 56, 28, 0, 68

Offset: 0

Author

Rémy Sigrist, Nov 11 2020

Keywords

• nonn
• base
• look

Comments

Leading zeros are ignored.

Links

• Rémy Sigrist, Table of n, a(n) for n = 0..6561

Crossrefs

Cf. A014190, A175919 (binary analog), A338827 (decimal analog).

Programs

Maple

a:= n-> (l-> (h-> add(h[j]*3^(j-1), j=1..nops(h)))([seq(
    abs(l[i]-l[-i]), i=1..nops(l))]))(convert(n, base, 3)):
seq(a(n), n=0..70);  # Alois P. Heinz, Nov 12 2020

PARI

a(n, base=3) = my (d=digits(n, base)); fromdigits(abs(d-Vecrev(d)), base)

Formula

a(n) = 0 iff n is a palindrome in base 3 (A014190).