OFFSET
1,1
COMMENTS
This is the fourth 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.
Assume that if w is any of the sequences u, v, u', v', then lim_{n->oo) w(n)/n exists and defines the (limiting) density of w. For w = u,v,u',v', denote the densities by r,s,r',s'. Then the densities of sequences (1)-(4) exist, and
1/(r*r') + 1/(r*s') + 1/(s*s') + 1/(s*r') = 1.
For A356141, u, v, u', v', are the Beatty sequences given by u(n) = floor(n*sqrt(2)) and v(n) = floor(n*(1/2 + sqrt(2)), so that r = sqrt(2), s = 1/2 + sqrt(2), r' = 2 + sqrt(2), s' = (9 + 4*sqrt(2))/7.
EXAMPLE
(1) v o u = (1, 3, 7, 9, 13, 15, 17, 21, 22, 26, 28, 30, 34, ...) = A356138
(2) v' o u = (2, 4, 8, 10, 14, 16, 18, 23, 25, 29, 31, 33, 37, ...) = A356139
(3) v o u' = (5, 11, 19, 24, 32, 38, 44, 51, 57, 65, 70, 76, 84, ...) = A356140
(4) v' o u' = (6, 12, 20, 27, 35, 41, 48, 56, 62, 71, 77, 83, 92, ...) = A356141
MATHEMATICA
z = 800;
u = Table[Floor[n (Sqrt[2])], {n, 1, z}]; (*A001951*)
u1 = Complement[Range[Max[u]], u] ; (*A001952*)
v = Table[Floor[n (1/2 + Sqrt[2])], {n, 1, z}]; (*A137803*)
v1 = Complement[Range[Max[v]], v] ; (*A137804*)
Table[v[[u[[n]]]], {n, 1, z/8}] (*A356138 *)
Table[v1[[u[[n]]]], {n, 1, z/8}] (* A356139*)
Table[v[[u1[[n]]]], {n, 1, z/8}] (* A356140 *)
Table[v1[[u1[[n]]]], {n, 1, z/8}] (* A356141 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Aug 06 2022
STATUS
approved