A212050 Number of (w,x,y,z) with all terms in {1,...,n} and 2w*x=5*y*z.

0, 0, 0, 0, 0, 20, 32, 36, 46, 54, 118, 126, 162, 170, 194, 316, 358, 370, 430, 442, 614, 666, 714, 730, 840, 1064, 1124, 1184, 1276, 1296, 1686, 1710, 1824, 1908, 1980, 2320, 2524, 2552, 2636, 2732, 3202, 3234, 3470, 3502, 3658, 4222, 4330

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[2 w*x == 5 y*z, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212050 *)
%/2  (* integers *)
(* Peter J. C. Moses, Apr 13 2012 *)