A211787 Number of (w,x,y,z) with all terms in {1,...,n} and w*x<=2*y*z.

0, 1, 15, 66, 201, 469, 958, 1735, 2937, 4656, 7050, 10242, 14461, 19813, 26569, 34904, 45086, 57293, 71898, 89050, 109201, 132534, 159424, 190167, 225296, 264966, 309685, 359823, 415889, 478142, 547302, 623514, 707593, 799821

Offset: 0

Author

Clark Kimberling, Apr 27 2012

Keywords

• nonn

Comments

a(n)+A211797(n)=n^4.

See A211795 for a guide to related sequences.

Links

• Bo Gyu Jeong, Table of n, a(n) for n = 0..200

Crossrefs

Cf. A211795.

Programs

Mathematica

t = Compile[{{n, _Integer}}, Module[{s = 0},
    (Do[If[w*x <= 2 y*z, s = s + 1],
    {w, 1, #}, {x, 1, #}, {y, 1, #},
      {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 40]] (* A211787 *)
(* Peter J. C. Moses, Apr 13 2012 *)