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A371268
If the ternary expansion of n starts with a 1, replace 1's by 2's, 2's by 0's, 0's by 1's, if it starts with a 2, replace 2's by 1's, 1's by 0's, 0's by 2's.
2
0, 2, 1, 7, 8, 6, 5, 3, 4, 22, 23, 21, 25, 26, 24, 19, 20, 18, 17, 15, 16, 11, 9, 10, 14, 12, 13, 67, 68, 66, 70, 71, 69, 64, 65, 63, 76, 77, 75, 79, 80, 78, 73, 74, 72, 58, 59, 57, 61, 62, 60, 55, 56, 54, 53, 51, 52, 47, 45, 46, 50, 48, 49, 35, 33, 34, 29, 27
OFFSET
0,2
COMMENTS
This sequence is a self-inverse permutation of the nonnegative integers.
FORMULA
A371256(a(n)) = A371256(n).
EXAMPLE
The first terms, in decimal and in base 3, are:
n a(n) ter(n) ter(a(n))
-- ---- ------ ---------
0 0 0 0
1 2 1 2
2 1 2 1
3 7 10 21
4 8 11 22
5 6 12 20
6 5 20 12
7 3 21 10
8 4 22 11
9 22 100 211
10 23 101 212
11 21 102 210
12 25 110 221
13 26 111 222
14 24 112 220
15 19 120 201
PROG
(PARI) a(n) = { my (d = digits(n, 3)); if (#d, d = if (d[1]==1, apply(v -> [1, 2, 0][1+v], d), apply(v -> [2, 0, 1][1+v], d)); ); fromdigits(d, 3); }
CROSSREFS
See A004488 and A361945 for similar sequences.
Sequence in context: A157240 A144749 A021463 * A371261 A199964 A217107
KEYWORD
nonn,base,easy
AUTHOR
Rémy Sigrist, Mar 16 2024
STATUS
approved