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A353660
The binary expansions of A352909(n+1, 1) and A352909(n+1, 2) encode respectively the 1's and the 2's in the ternary expansion of a(n).
3
0, 2, 1, 6, 3, 8, 7, 5, 4, 18, 9, 20, 19, 11, 10, 24, 21, 15, 12, 26, 25, 23, 22, 17, 16, 14, 13, 54, 27, 56, 55, 29, 28, 60, 57, 33, 30, 62, 61, 59, 58, 35, 34, 32, 31, 72, 63, 45, 36, 74, 73, 65, 64, 47, 46, 38, 37, 78, 75, 69, 66, 51, 48, 42, 39, 80, 79, 77
OFFSET
0,2
COMMENTS
This sequence is a permutation of the nonnegative integers with inverse A353661.
FORMULA
a(n) = A005836(A352909(n+1, 1)) + 2*A005836(A352909(n+1, 2)).
a(n) < 3^k iff n < 3^k.
EXAMPLE
For n = 42:
- A352909(43, 1) = 9,
- A352909(43, 2) = 2,
- the binary expansion of 9 is "1001",
- the binary expansion of 2 is "10",
- so the ternary expansion of a(42) is "1021",
- and a(42) = 34.
PROG
(PARI) b2t(n) = fromdigits(binary(n), 3)
{ n=-1; for (d=0, 2^8-1, for (k=0, d, if (bitand(t1=k, t2=d-k)==0, print1 (b2t(t1) + 2*b2t(t2)", "); if (n++==67, break (2))))) }
CROSSREFS
Cf. A005836, A352909, A353661 (inverse), A353662.
Sequence in context: A293182 A124441 A284475 * A285355 A316605 A307178
KEYWORD
nonn,look,base
AUTHOR
Rémy Sigrist, May 02 2022
STATUS
approved