A212049 Number of (w,x,y,z) with all terms in {1,...,n} and w*x=5*y*z.

0, 0, 0, 0, 0, 18, 26, 30, 38, 44, 108, 116, 144, 152, 172, 280, 314, 326, 372, 384, 564, 612, 652, 668, 752, 954, 1002, 1056, 1136, 1156, 1528, 1552, 1642, 1718, 1778, 2084, 2250, 2278, 2346, 2430, 2922, 2954, 3150, 3182, 3318, 3830, 3918, 3954

Offset: 0

Author

Clark Kimberling, Apr 29 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 == 5 y*z, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212049 *)
%/2  (* integers *)
(* Peter J. C. Moses, Apr 13 2012 *)