A211919 Number of (w,x,y,z) with all terms in {1,...,n} and w*x>=3*y*z.

0, 0, 1, 14, 46, 118, 267, 497, 871, 1438, 2215, 3273, 4713, 6526, 8844, 11758, 15303, 19590, 24796, 30862, 38053, 46457, 56115, 67206, 79971, 94357, 110628, 128979, 149481, 172291, 197776, 225789, 256763, 290878, 328179, 369011

Offset

0,4

Comments

a(n)+A211920(n)=n^4.

See A211795 for a guide to related sequences.

Links

Table of n, a(n) for n=0..35.

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, 40]] (* A211919 *)
(* Peter J. C. Moses, Apr 13 2012 *)

Crossrefs

Cf. A211795.

Sequence in context: A043191 A043971 A233367 * A233361 A243039 A243385

Adjacent sequences: A211916 A211917 A211918 * A211920 A211921 A211922

Keyword

nonn

Author

Clark Kimberling, Apr 28 2012

Status

approved