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A212256 Number of (w,x,y,z) with all terms in {1,...,n} and 4/w = 1/x + 1/y + 1/z + 1/n. 2

%I

%S 0,1,1,4,13,1,22,1,13,10,22,1,61,1,18,102,13,1,82,1,156,79,1,1,184,1,

%T 1,10,183,1,297,1,13,105,1,181,298,1,1,16,285,1,378,1,64,405,1,1,358,

%U 1,37,13,96,1,163,130,402,31,1,1,944

%N Number of (w,x,y,z) with all terms in {1,...,n} and 4/w = 1/x + 1/y + 1/z + 1/n.

%C w = harmonic mean of {x,y,z,n}. For a guide to related sequences, see A211795.

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

%t (Do[If[4/w == 1/x + 1/y + 1/z + 1/n, s = s + 1],

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

%t Map[t[#] &, Range[0, 60]] (* A212256 *)

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

%Y Cf. A211795.

%K nonn

%O 0,4

%A _Clark Kimberling_, May 15 2012

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Last modified January 19 12:36 EST 2020. Contains 331049 sequences. (Running on oeis4.)