A211265 Number of integer pairs (x,y) such that 0

0, 1, 2, 3, 5, 6, 8, 9, 11, 12, 15, 16, 18, 20, 22, 23, 26, 27, 30, 32, 34, 35, 39, 40, 42, 44, 47, 48, 52, 53, 56, 58, 60, 62, 66, 67, 69, 71, 75, 76, 80, 81, 84, 87, 89, 90, 95, 96, 99, 101, 104, 105, 109, 111, 115, 117, 119, 120, 126, 127, 129, 132, 135, 137

Offset: 1

Author

Clark Kimberling, Apr 06 2012

Keywords

• nonn

Comments

For a guide to related sequences, see A211266.

Crossrefs

Cf. A211266.

Programs

Mathematica

a = 1; b = n; z1 = 120;
t[n_] := t[n] = Flatten[Table[x*y, {x, a, b - 1},
 {y, x + 1, b}]]
c[n_, k_] := c[n, k] = Count[t[n], k]
Table[c[n, n], {n, 1, z1}]           (* A056924 *)
Table[c[n, n + 1], {n, 1, z1}]       (* A211159 *)
Table[c[n, 2*n], {n, 1, z1}]         (* A211261 *)
Table[c[n, 3*n], {n, 1, z1}]         (* A211262 *)
Table[c[n, Floor[n/2]], {n, 1, z1}]  (* A211263 *)
Print
c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, a, m}]
Table[c1[n, n], {n, 1, z1}]          (* A211264 *)
Table[c1[n, n + 1], {n, 1, z1}]      (* A211265 *)
Table[c1[n, 2*n], {n, 1, z1}]        (* A211266 *)
Table[c1[n, 3*n], {n, 1, z1}]        (* A211267 *)
Table[c1[n, Floor[n/2]], {n, 1, z1}] (* A181972 *)