A212047 Number of (w,x,y,z) with all terms in {1,...,n} and w*x=4*y*z.

0, 0, 1, 1, 14, 18, 31, 35, 80, 96, 125, 133, 216, 228, 269, 309, 444, 460, 543, 559, 720, 784, 853, 873, 1142, 1202, 1287, 1363, 1596, 1624, 1831, 1859, 2206, 2314, 2427, 2559, 2962, 2998, 3123, 3247, 3758, 3798, 4103, 4143, 4524, 4772, 4925, 4969, 5712, 5836

Offset: 0

Author

Clark Kimberling, Apr 28 2012

Keywords

• nonn

Comments

See A211795 for a guide to related sequences.

Crossrefs

Cf. A211795.

Programs

Mathematica

t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*x == 4 y*z, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212047 *)
(* Peter J. C. Moses, Apr 13 2012 *)