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URL: https://oeis.org/A361832

⇱ A361832 - OEIS

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A361832
For any number k >= 0, let T_k be the triangle whose base corresponds to the ternary expansion of k (without leading zeros) and other values, say t above u and v, satisfy t = (-u-v) mod 3; the ternary expansion of a(n) corresponds to the left border of T_n (the most significant digit being at the bottom left corner).
3
0, 1, 2, 5, 4, 3, 7, 6, 8, 16, 17, 15, 12, 13, 14, 11, 9, 10, 23, 21, 22, 19, 20, 18, 24, 25, 26, 50, 49, 48, 53, 52, 51, 47, 46, 45, 38, 37, 36, 41, 40, 39, 44, 43, 42, 35, 34, 33, 29, 28, 27, 32, 31, 30, 70, 69, 71, 64, 63, 65, 67, 66, 68, 58, 57, 59, 61, 60
OFFSET
0,3
COMMENTS
This sequence is a variant of A334727.
This sequence is a self-inverse permutation of the nonnegative integers that preserves the number of digits and the leading digit in base 3.
FORMULA
a(floor(n/3)) = floor(a(n)/3).
a(A004488(n)) = A004488(a(n)).
a(n) = n for any n in A048328.
a(n) = n iff b belongs to A361833.
EXAMPLE
For n = 42: the ternary expansion of 42 is "1120" and the corresponding triangle is as follows:
2
2 2
1 0 1
1 1 2 0
So the ternary expansion of a(42) is "1122", and a(42) = 44.
PROG
(PARI) a(n) = { my (d = digits(n, 3), t = vector(#d)); for (k = 1, #d, t[k] = d[1]; d = vector(#d-1, i, (-d[i]-d[i+1]) % 3); ); fromdigits(t, 3); }
CROSSREFS
Cf. A004488, A048328, A334727, A361818, A361833 (fixed points).
Sequence in context: A328626 A265357 A265358 * A361945 A171837 A216253
KEYWORD
nonn,base
AUTHOR
Rémy Sigrist, Mar 26 2023
STATUS
approved