cp's OEIS Frontend

A212105 Number of (w,x,y,z) with all terms in {1,...,n} and w > harmonic mean of {x,y,z}.

%I A212105 #10 Dec 04 2016 19:46:29
%S A212105 0,0,7,45,150,373,768,1437,2479,4002,6120,9010,12786,17661,23821,
%T A212105 31464,40809,52102,65577,81531,100201,121911,146979,175717,208434,
%U A212105 245550,287401,334380,386877,445366,510222,581922,660952,747750,842850
%N A212105 Number of (w,x,y,z) with all terms in {1,...,n} and w > harmonic mean of {x,y,z}.
%C A212105 a(n)+A212104(n)=n^4.
%C A212105 A 4-tuple (w,x,y,z) is counted if 3/w>1/x+1/y+1/z.
%C A212105 For a guide to related sequences, see A211795.
%t A212105 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212105 (Do[If[w*(y*z + z*x + x*y) > 3 x*y*z, s = s + 1],
%t A212105 {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t A212105 Map[t[#] &, Range[0, 40]] (* A212105 *)
%t A212105 (* _Peter J. C. Moses_, Apr 13 2012 *)
%Y A212105 Cf. A211795, A212103.
%K A212105 nonn
%O A212105 0,3
%A A212105 _Clark Kimberling_, May 04 2012