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 A211274 Number of integer pairs (x,y) such that 0 < x <= y <= n and x*y <= 3n. 7
 0, 2, 5, 9, 12, 16, 20, 24, 28, 33, 37, 43, 46, 52, 57, 62, 67, 72, 78, 84, 88, 95, 99, 107, 111, 117, 124, 130, 134, 142, 147, 154, 159, 166, 173, 179, 184, 191, 197, 206, 210, 218, 223, 231, 237, 243, 250, 259, 264, 271, 277, 286, 289, 299, 305, 313 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For a guide to related sequences, see A211266. LINKS EXAMPLE a(4) counts these pairs: (1,1), (1,2), (1,3), (1,4), (2,3), (2,4), (3,3,), (3,4), (4,4). MATHEMATICA a = 1; b = n; z1 = 120; t[n_] :=  t[n] = Flatten[Table[x*y, {x, a, b - 1}, {y, x, b}]] c[n_, k_] := c[n, k] = Count[t[n], k] Table[c[n, n], {n, 1, z1}]           (* A038548 *) Table[c[n, n + 1], {n, 1, z1}]       (* A072670 *) Table[c[n, 2*n], {n, 1, z1}]         (* A211270 *) Table[c[n, 3*n], {n, 1, z1}]         (* A211271 *) Table[c[n, Floor[n/2]], {n, 1, z1}]  (* A211272 *) c1[n_, m_] := c1[n, m] = Sum[c[n, k], {k, a, m}] Print Table[c1[n, n], {n, 1, z1}]          (* A094820 *) Table[c1[n, n + 1], {n, 1, z1}]      (* A091627 *) Table[c1[n, 2*n], {n, 1, z1}]        (* A211273 *) Table[c1[n, 3*n], {n, 1, z1}]        (* A211274 *) Table[c1[n, Floor[n/2]], {n, 1, z1}] (* A211275 *) CROSSREFS Cf. A211266. Sequence in context: A047385 A284624 A086814 * A276217 A086343 A056549 Adjacent sequences:  A211271 A211272 A211273 * A211275 A211276 A211277 KEYWORD nonn AUTHOR Clark Kimberling, Apr 07 2012 STATUS approved

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Last modified May 24 13:34 EDT 2022. Contains 354033 sequences. (Running on oeis4.)