cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A305878 For any number n >= 0: apply the map 0 -> "0", 1 -> "01", 2 -> "011" to the ternary representation of n and interpret the result as a binary string.

Original entry on oeis.org

0, 1, 3, 2, 5, 11, 6, 13, 27, 4, 9, 19, 10, 21, 43, 22, 45, 91, 12, 25, 51, 26, 53, 107, 54, 109, 219, 8, 17, 35, 18, 37, 75, 38, 77, 155, 20, 41, 83, 42, 85, 171, 86, 173, 347, 44, 89, 179, 90, 181, 363, 182, 365, 731, 24, 49, 99, 50, 101, 203, 102, 205, 411
Offset: 0

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Author

Rémy Sigrist, Jun 13 2018

Keywords

Comments

This sequence is a ternary analog of A048678.
This sequence is a permutation of A003726.

Examples

			The first terms, alongside the ternary representation of n and the binary representation of a(n), are:
  n   a(n)  tern(n)  bin(a(n))
  --  ----  -------  ---------
   0     0        0          0
   1     1        1          1
   2     3        2         11
   3     2       10         10
   4     5       11        101
   5    11       12       1011
   6     6       20        110
   7    13       21       1101
   8    27       22      11011
   9     4      100        100
  10     9      101       1001
  11    19      102      10011
  12    10      110       1010
		

Crossrefs

Programs

  • PARI
    a(n) = if (n==0, 0, my (d=n%3); a(n\3) * 2^(d+1) + (2^d-1))

Formula

a(0) = 0.
a(3*n) = 2*a(n).
a(3*n + 1) = 4*a(n) + 1.
a(3*n + 2) = 8*a(n) + 3.
A000120(a(n)) = A053735(n).