|
%I #9 Dec 04 2016 19:46:28
%S 0,0,4,8,24,32,64,76,124,154,214,234,340,364,452,532,664,696,854,890,
%T 1086,1206,1350,1394,1692,1794,1966,2108,2396,2452,2822,2882,3212,
%U 3408,3636,3860,4360,4432,4688,4920,5470,5550,6090,6174,6642,7056
%N Number of (w,x,y,z) with all terms in {1,...,n} and w*x=2*y*z.
%C Each term is divisible by 2. See A211795 for a guide to related sequences.
%H Bo Gyu Jeong, <a href="/A212019/b212019.txt">Table of n, a(n) for n = 0..200</a>
%e a(2) counts these four 4-tuples: (1,2,1,1), (2,1,1,1), (2,2,1,2), (2,2,2,1).
%t t = Compile[{{n, _Integer}}, Module[{s = 0},
%t (Do[If[w*x == 2 y*z, s = s + 1],
%t {w, 1, #}, {x, 1, #}, {y, 1, #}, {z, 1, #}] &[n]; s)]];
%t Map[t[#] &, Range[0, 60]] (* A212019 *)
%t %/2 (* integers *)
%t (* _Peter J. C. Moses_, Apr 13 2012 *)
%Y Cf. A211795.
%K nonn
%O 0,3
%A _Clark Kimberling_, Apr 28 2012
|
