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Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x>2*y*z.
3

%I #11 Dec 04 2016 19:46:28

%S 0,0,1,15,55,156,338,666,1159,1905,2950,4399,6275,8748,11847,15721,

%T 20450,26228,33078,41271,50799,61947,74832,89674,106480,125659,147291,

%U 171618,198767,229139,262698,300007,340983,386100,435544,489598

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

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

%C See A211795 for a guide to related sequences.

%H Bo Gyu Jeong, <a href="/A211797/b211797.txt">Table of n, a(n) for n = 0..200</a>

%t t = Compile[{{n, _Integer}}, Module[{s = 0},

%t (Do[If[w*x > 2 y*z, s = s + 1], {w, 1, #},

%t {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];

%t Map[t[#] &, Range[0, 40]] (* A211797 *)

%t (* _Peter J. C. Moses_, Apr 13 2012 *)

%Y Cf. A211795.

%K nonn

%O 0,4

%A _Clark Kimberling_, Apr 27 2012