A374363 a(n) is the greatest term t <= n of A005836 such that n - t also belongs to A005836.

0, 1, 1, 3, 4, 4, 3, 4, 4, 9, 10, 10, 12, 13, 13, 12, 13, 13, 9, 10, 10, 12, 13, 13, 12, 13, 13, 27, 28, 28, 30, 31, 31, 30, 31, 31, 36, 37, 37, 39, 40, 40, 39, 40, 40, 36, 37, 37, 39, 40, 40, 39, 40, 40, 27, 28, 28, 30, 31, 31, 30, 31, 31, 36, 37, 37, 39, 40

Offset: 0

Author

Rémy Sigrist, Jul 06 2024

Keywords

• nonn
• base

Comments

To compute a(n): in the ternary expansion of n, 2's by 1's.

Examples

			The first terms, in decimal and in ternary, are:
  n   a(n)  ter(n)  ter(a(n))
  --  ----  ------  ---------
   0     0       0          0
   1     1       1          1
   2     1       2          1
   3     3      10         10
   4     4      11         11
   5     4      12         11
   6     3      20         10
   7     4      21         11
   8     4      22         11
   9     9     100        100
  10    10     101        101
  11    10     102        101
  12    12     110        110
  13    13     111        111
  14    13     112        111
  15    12     120        110
		

Links

• Rémy Sigrist, Table of n, a(n) for n = 0..6560

Crossrefs

Cf. A005836, A120880, A289831, A374361, A374362.

Programs

PARI

a(n) = fromdigits(apply(d -> [0, 1, 1][1+d], digits(n, 3)), 3)

Formula

a(n) = T(n, A120880(k)-1).

a(n) = n - A374362(n).

a(n) <= n with equality iff n belongs to A005836.

a(n) = A005836(1+A289831(n)).