cp's OEIS Frontend

A212107 Number of (w,x,y,z) with all terms in {1,...,n} and w >= harmonic mean of {x,y,z}.

%I A212107 #9 Dec 04 2016 19:46:29
%S A212107 0,1,9,48,160,384,798,1468,2517,4041,6172,9063,12870,17746,23907,
%T A212107 31581,40933,52227,65721,81676,100401,122136,147205,175944,208716,
%U A212107 245833,287685,334665,387211,445701,510642,582343,661380,748185,843286
%N A212107 Number of (w,x,y,z) with all terms in {1,...,n} and w >= harmonic mean of {x,y,z}.
%C A212107 a(n)+A212106(n)=n^4.
%C A212107 A 4-tuple (w,x,y,z) is counted if 3/w>=1/x+1/y+1/z.
%C A212107 For a guide to related sequences, see A211795.
%t A212107 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212107 (Do[If[w*(y*z + z*x + x*y) >= 3 x*y*z, s = s + 1],
%t A212107 {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t A212107 Map[t[#] &, Range[0, 40]] (* A212107 *)
%t A212107 (* _Peter J. C. Moses_, Apr 13 2012 *)
%Y A212107 Cf. A211795, A212103.
%K A212107 nonn
%O A212107 0,3
%A A212107 _Clark Kimberling_, May 04 2012