A211797 Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x>2*y*z.

0, 0, 1, 15, 55, 156, 338, 666, 1159, 1905, 2950, 4399, 6275, 8748, 11847, 15721, 20450, 26228, 33078, 41271, 50799, 61947, 74832, 89674, 106480, 125659, 147291, 171618, 198767, 229139, 262698, 300007, 340983, 386100, 435544, 489598

Offset

0,4

Comments

a(n)+A211787(n)=n^4.

See A211795 for a guide to related sequences.

Links

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

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]] (* A211797 *)
(* Peter J. C. Moses, Apr 13 2012 *)

Crossrefs

Cf. A211795.

Sequence in context: A179741 A144312 A062025 * A172436 A119134 A119658

Adjacent sequences: A211794 A211795 A211796 * A211798 A211799 A211800

Keyword

nonn

Author

Clark Kimberling, Apr 27 2012

Status

approved