A180200 -id:A180200 - cp's OEIS frontend

A273494 a(n) = A245325(n) + A245326(n).

2, 3, 3, 5, 4, 5, 4, 8, 7, 7, 5, 8, 7, 7, 5, 13, 11, 12, 9, 11, 10, 9, 6, 13, 11, 12, 9, 11, 10, 9, 6, 21, 18, 19, 14, 19, 17, 16, 11, 18, 15, 17, 13, 14, 13, 11, 7, 21, 18, 19, 14, 19, 17, 16, 11, 18, 15, 17, 13, 14, 13, 11, 7, 34, 29, 31, 23, 30, 27, 25, 17, 31, 26, 29, 22, 25, 23, 20, 13, 29, 25, 26, 19, 27, 24, 23, 16, 23

Offset: 1

Yosu Yurramendi, May 23 2016

nonn

The terms (n>0) may be written as a left-justified array with rows of length 2^m, m >= 0:
   2,
   3, 3,
   5, 4, 5, 4,
   8, 7, 7, 5, 8, 7, 7, 5,
  13,11,12, 9,11,10, 9, 6,13,11,12, 9,11,10, 9, 6,
  21,18,19,14,19,17,16,11,18,15,17,13,14,13,11, 7,21,18,19,14,19,17,...
All columns have the Fibonacci sequence property: a(2^(m+2) + k) = a(2^(m+1) + k) + a(2^m + k), m >= 0, 0 <= k < 2^m (empirical observations).
The terms (n>0) may also be written as a right-justified array with rows of length 2^m, m >= 0:
                                                                           2,
                                                                        3, 3,
                                                                  5, 4, 5, 4,
                                                      8, 7, 7, 5, 8, 7, 7, 5,
                             13,11,12, 9,11,10, 9, 6,13,11,12, 9,11,10, 9, 6,
..., 18,15,17,13,14,13,11, 7,21,18,19,14,19,17,16,11,18,15,17,13,14,13,11, 7,
Each column is an arithmetic sequence. The differences of the arithmetic sequences give the sequence A071585: a(2^(m+1)-1-k) - a(2^m-1-k) = A071585(k), m >= 0, 0 <= k < 2^m.
n > 1 occurs in this sequence phi(n) = A000010(n) times, as it occurs in A007306 (Franklin T. Adams-Watters's comment), which is the sequence obtained by adding numerator and denominator in the Calkin-Wilf enumeration system of positive rationals. A245325(n)/A245326(n) is also an enumeration system of all positive rationals, and in each level m >= 0 (ranks between 2^m and 2^(m+1)-1) rationals are the same in both systems. Thus a(n) has the same terms in each level as A007306.
The same property occurs in all numerator+denominator sequences of enumeration systems of positive rationals, as, for example, A007306 (A007305+A047679), A071585 (A229742+A071766), A086592 (A020650+A020651), A268087 (A162909+A162910).

Yosu Yurramendi, Table of n, a(n) for n = 1..4095

Cf. A007306, A268087, A071585, A086592, A273493

a(n) = my(x=1, y=1); for(i=0, logint(n, 2), if(bittest(n, i), [x, y]=[x+y, y], [x, y]=[y, x+y])); x \\ Mikhail Kurkov, Mar 10 2023

a(n) = A273493(A059893(n)), a(A059893(n)) = A273493(n), n > 0. - Yosu Yurramendi, May 30 2017

a(n) = A007306(A059893(A180200(n))) = A007306(A059894(A154435(n))). - Yosu Yurramendi, Sep 20 2021

A335858 Nonnegative integers ordered by binary length and then lexicographically by run lengths (considering least significant runs first).

Original entry on oeis.org

0, 1, 2, 3, 5, 6, 4, 7, 10, 13, 9, 14, 11, 12, 8, 15, 21, 26, 18, 29, 22, 25, 17, 30, 20, 27, 19, 28, 23, 24, 16, 31, 42, 53, 37, 58, 45, 50, 34, 61, 41, 54, 38, 57, 46, 49, 33, 62, 43, 52, 36, 59, 44, 51, 35, 60, 40, 55, 39, 56, 47, 48, 32, 63, 85, 106, 74

Offset: 0

Rémy Sigrist, Jun 27 2020

The variant where we consider most significant runs first apparently corresponds to A180200.

			The first terms, alongside the corresponding binary representation and run lengths, are:
  n   a(n)  bin(a(n))  A227736(n, *)
  --  ----  ---------  -------------
   0     0          0  ()
   1     1          1  (1)
   2     2         10  (1, 1)
   3     3         11  (2)
   4     5        101  (1, 1, 1)
   5     6        110  (1, 2)
   6     4        100  (2, 1)
   7     7        111  (3)
   8    10       1010  (1, 1, 1, 1)
   9    13       1101  (1, 1, 2)
  10     9       1001  (1, 2, 1)
  11    14       1110  (1, 3)
  12    11       1011  (2, 1, 1)
  13    12       1100  (2, 2)
  14     8       1000  (3, 1)
  15    15       1111  (4)

Rémy Sigrist, Table of n, a(n) for n = 0..8192
Rémy Sigrist, PARI program for A335858
Index entries for sequences related to binary expansion of n
Index entries for sequences that are permutations of the natural numbers

Cf. A005811, A180200, A227736.

PARI
```
See Links section.
```

Apparently a(n) = A056539(A180200(n)).

cp's OEIS Frontend

A273494 a(n) = A245325(n) + A245326(n).

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

PARI

Formula