cp's OEIS Frontend

A212106 Number of (w,x,y,z) with all terms in {1,...,n} and w < harmonic mean of {x,y,z}.

%I A212106 #8 Dec 04 2016 19:46:29
%S A212106 0,0,7,33,96,241,498,933,1579,2520,3828,5578,7866,10815,14509,19044,
%T A212106 24603,31294,39255,48645,59599,72345,87051,103897,123060,144792,
%U A212106 169291,196776,227445,261580,299358,341178,387196,437736,493050
%N A212106 Number of (w,x,y,z) with all terms in {1,...,n} and w < harmonic mean of {x,y,z}.
%C A212106 a(n)+A212107(n)=n^4.
%C A212106 A 4-tuple (w,x,y,z) is counted if 3/w<1/x+1/y+1/z.
%C A212106 For a guide to related sequences, see A211795.
%t A212106 t = Compile[{{n, _Integer}}, Module[{s = 0},
%t A212106 (Do[If[w*(y*z + z*x + x*y) < 3 x*y*z, s = s + 1],
%t A212106 {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t A212106 Map[t[#] &, Range[0, 40]] (* A212106 *)
%t A212106 (* _Peter J. C. Moses_, Apr 13 2012 *)
%Y A212106 Cf. A211795, A212103.
%K A212106 nonn
%O A212106 0,3
%A A212106 _Clark Kimberling_, May 04 2012