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A211809 Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x >= 2*y*z.

%I A211809 #12 Apr 26 2020 20:37:06
%S A211809 0,0,5,23,79,188,402,742,1283,2059,3164,4633,6615,9112,12299,16253,
%T A211809 21114,26924,33932,42161,51885,63153,76182,91068,108172,127453,149257,
%U A211809 173726,201163,231591,265520,302889,344195,389508,439180,493458
%N A211809 Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x >= 2*y*z.
%C A211809 a(n) + A211795(n) = n^4.
%C A211809 See A211795 for a guide to related sequences.
%H A211809 Bo Gyu Jeong, <a href="/A211809/b211809.txt">Table of n, a(n) for n = 0..200</a>
%t A211809 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A211809 (Do[If[w*x >= 2 y*z, s = s + 1],
%t A211809 {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t A211809 Map[t[#] &, Range[0, 40]] (* A211809 *)
%t A211809 (* _Peter J. C. Moses_, Apr 13 2012 *)
%Y A211809 Cf. A211795.
%K A211809 nonn
%O A211809 0,3
%A A211809 _Clark Kimberling_, Apr 27 2012