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A211265 Number of integer pairs (x,y) such that 0 and x*y<=n+1.

%I A211265 #4 Apr 11 2012 18:49:52
%S A211265 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,
%T A211265 44,47,48,52,53,56,58,60,62,66,67,69,71,75,76,80,81,84,87,89,90,95,96,
%U A211265 99,101,104,105,109,111,115,117,119,120,126,127,129,132,135,137
%N A211265 Number of integer pairs (x,y) such that 0<x<y<=n and x*y<=n+1.
%C A211265 For a guide to related sequences, see A211266.
%t A211265 a = 1; b = n; z1 = 120;
%t A211265 t[n_] := t[n] = Flatten[Table[x*y, {x, a, b - 1},
%t A211265  {y, x + 1, b}]]
%t A211265 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211265 Table[c[n, n], {n, 1, z1}]           (* A056924 *)
%t A211265 Table[c[n, n + 1], {n, 1, z1}]       (* A211159 *)
%t A211265 Table[c[n, 2*n], {n, 1, z1}]         (* A211261 *)
%t A211265 Table[c[n, 3*n], {n, 1, z1}]         (* A211262 *)
%t A211265 Table[c[n, Floor[n/2]], {n, 1, z1}]  (* A211263 *)
%t A211265 Print
%t A211265 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, a, m}]
%t A211265 Table[c1[n, n], {n, 1, z1}]          (* A211264 *)
%t A211265 Table[c1[n, n + 1], {n, 1, z1}]      (* A211265 *)
%t A211265 Table[c1[n, 2*n], {n, 1, z1}]        (* A211266 *)
%t A211265 Table[c1[n, 3*n], {n, 1, z1}]        (* A211267 *)
%t A211265 Table[c1[n, Floor[n/2]], {n, 1, z1}] (* A181972 *)
%Y A211265 Cf. A211266.
%K A211265 nonn
%O A211265 1,3
%A A211265 _Clark Kimberling_, Apr 06 2012