A212020 Number of (w,x,y,z) with all terms in {1,...,n} and w*x=3*y*z.

0, 0, 0, 8, 14, 18, 48, 56, 74, 126, 154, 166, 262, 278, 318, 422, 480, 500, 674, 698, 800, 956, 1024, 1052, 1308, 1378, 1458, 1698, 1852, 1888, 2240, 2280, 2434, 2686, 2794, 2950, 3472, 3520, 3640, 3944, 4234, 4286, 4800, 4856, 5102, 5672

Offset: 0

Author

Clark Kimberling, Apr 28 2012

Keywords

• nonn

Comments

Each term is divisible by 2. See A211795 for a guide to related sequences.

Crossrefs

Cf. A211795.

Programs

Mathematica

t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*x == 3 y*z, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212020 *)
%/2  (* integers *)
(* Peter J. C. Moses, Apr 13 2012 *)