A360136 a(n) = 1 + A026430(A026430(n)).

2, 6, 9, 10, 13, 15, 16, 19, 22, 24, 25, 28, 29, 32, 36, 37, 40, 42, 43, 46, 47, 51, 53, 55, 56, 60, 62, 64, 67, 69, 70, 73, 76, 78, 79, 82, 83, 87, 89, 91, 92, 96, 99, 100, 103, 104, 106, 109, 110, 114, 117, 118, 121, 122, 124, 127, 130, 131, 133, 136, 137

Offset

1,1

Comments

This is the first of four sequences that partition the positive integers. Suppose that u = (u(n)) and v = (v(n)) are increasing sequences of positive integers. Let u' and v' be their (increasing) complements, and consider these four sequences:

(1) v o u, defined by (v o u)(n) = v(u(n));

(2) v' o u;

(3) v o u';

(4) v' o u.

Every positive integer is in exactly one of the four sequences. Their limiting densities are 4/9, 2/9, 2/9, 1/9, respectively.

Links

Table of n, a(n) for n=1..61.

Example

(1)  v o u = (2, 6, 9, 10, 13, 15, 16, 19, 22, 24, 25, 28, 29, 32, 36, ...) = A360136
(2)  v' o u = (1, 5, 12, 14, 21, 23, 26, 33, 39, 41, 44, 50, 54, 59, 65, ...) = A360137
(3)  v o u' = (4, 7, 11, 17, 20, 27, 31, 34, 38, 45, 49, 52, 58, 61, 66, ...) = A360138
(4)  v' o u' = (3, 8, 18, 30, 35, 48, 57, 63, 72, 84, 93, 98, 111, 116, ...) = A360139

Mathematica

z = 2000; zz = 100;
u = Accumulate[1 + ThueMorse /@ Range[0, 600]]; (* A026430 *)
u1 = Complement[Range[Max[u]], u];  (* A356133 *)
v = u + 1;  (* A285954 *)
v1 = Complement[Range[Max[v]], v];   (* A285953 *)
Table[v[[u[[n]]]], {n, 1, zz}]       (* A360136 *)
Table[v1[[u[[n]]]], {n, 1, zz}]      (* A360137 *)
Table[v[[u1[[n]]]], {n, 1, zz}]      (* A360138 *)
Table[v1[[u1[[n]]]], {n, 1, zz}]     (* A360139 *)

Prog

(Python)
def A360136(n): return 1+(m:=n+(n-1>>1)+(n-1&1|(n.bit_count()&1^1)))+(m-1>>1)+(m-1&1|(m.bit_count()&1^1)) # Chai Wah Wu, Mar 01 2023

Crossrefs

Cf. A026530, A359352, A285953, A359277 (intersections instead of results of composition), A359352-A360135, A360137-A360139.

Sequence in context: A285532 A350944 A016726 * A359821 A047396 A276936

Adjacent sequences: A360133 A360134 A360135 * A360137 A360138 A360139

Keyword

nonn,easy

Author

Clark Kimberling, Feb 03 2023

Status

approved