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A211275 Number of integer pairs (x,y) such that 0 < x <= y <= n and x*y <= floor(n/2).

%I A211275 #6 Dec 21 2015 04:26:59
%S A211275 0,1,1,2,2,3,3,5,5,6,6,8,8,9,9,11,11,13,13,15,15,16,16,19,19,20,20,22,
%T A211275 22,24,24,27,27,28,28,31,31,32,32,35,35,37,37,39,39,40,40,44,44,46,46,
%U A211275 48,48,50,50,53,53,54,54,58,58,59,59,62,62,64,64,66,66,68,68
%N A211275 Number of integer pairs (x,y) such that 0 < x <= y <= n and x*y <= floor(n/2).
%C A211275 For a guide to related sequences, see A211266.
%t A211275 a = 1; b = n; z1 = 120;
%t A211275 t[n_] :=  t[n] = Flatten[Table[x*y, {x, a, b - 1},
%t A211275 {y, x, b}]]
%t A211275 c[n_, k_] := c[n, k] = Count[t[n], k]
%t A211275 Table[c[n, n], {n, 1, z1}]           (* A038548 *)
%t A211275 Table[c[n, n + 1], {n, 1, z1}]       (* A072670 *)
%t A211275 Table[c[n, 2*n], {n, 1, z1}]         (* A211270 *)
%t A211275 Table[c[n, 3*n], {n, 1, z1}]         (* A211271 *)
%t A211275 Table[c[n, Floor[n/2]], {n, 1, z1}]  (* A211272 *)
%t A211275 c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, a, m}]
%t A211275 Print
%t A211275 Table[c1[n, n], {n, 1, z1}]          (* A094820 *)
%t A211275 Table[c1[n, n + 1], {n, 1, z1}]      (* A091627 *)
%t A211275 Table[c1[n, 2*n], {n, 1, z1}]        (* A211273 *)
%t A211275 Table[c1[n, 3*n], {n, 1, z1}]        (* A211274 *)
%t A211275 Table[c1[n, Floor[n/2]], {n, 1, z1}] (* A211275 *)
%Y A211275 Cf. A211266.
%K A211275 nonn
%O A211275 1,4
%A A211275 _Clark Kimberling_, Apr 07 2012