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

%I #12 Dec 04 2016 19:46:28

%S 0,1,11,50,160,387,792,1480,2511,4001,6104,8943,12623,17396,23374,

%T 30765,39803,50707,63656,79050,96985,117795,141871,169444,200754,

%U 236327,276397,321322,371547,427471,489342,557906,633285,716040,806754

%N Number of (w,x,y,z) with all terms in {1,...,n} and 2*w*x<3*y*z.

%C a(n)+A211923(n)=n^4.

%C See A211795 for a guide to related sequences.

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

%t (Do[If[2 w*x < 3 y*z, s = s + 1],

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

%t Map[t[#] &, Range[0, 40]] (* A211920 *)

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

%Y Cf. A211795.

%K nonn

%O 0,3

%A _Clark Kimberling_, Apr 28 2012