A212053 Number of (w,x,y,z) with all terms in {1,...,n} and w*x<=y*z+1.

0, 1, 13, 56, 158, 365, 725, 1312, 2198, 3477, 5245, 7624, 10742, 14725, 19725, 25920, 33470, 42557, 53397, 66176, 81150, 98525, 118533, 141456, 167606, 197189, 230509, 267920, 309726, 356205, 407805, 464744, 527494, 596389, 671789

Offset: 0

Author

Clark Kimberling, Apr 29 2012

Keywords

• nonn

Comments

a(n)+A212054(n)=n^4. See A211795 for a guide to related sequences.

Crossrefs

Cf. A211795.

Programs

Mathematica

t = Compile[{{n, _Integer}}, Module[{s = 0},
(Do[If[w*x <= y*z + 1, s = s + 1],
{w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
Map[t[#] &, Range[0, 50]] (* A212053 *)
(* Peter J. C. Moses, Apr 13 2012 *)