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A212020 Number of (w,x,y,z) with all terms in {1,...,n} and w*x=3*y*z. 2
0, 0, 0, 8, 14, 18, 48, 56, 74, 126, 154, 166, 262, 278, 318, 422, 480, 500, 674, 698, 800, 956, 1024, 1052, 1308, 1378, 1458, 1698, 1852, 1888, 2240, 2280, 2434, 2686, 2794, 2950, 3472, 3520, 3640, 3944, 4234, 4286, 4800, 4856, 5102, 5672 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Each term is divisible by 2.  See A211795 for a guide to related sequences.

LINKS

Table of n, a(n) for n=0..45.

MATHEMATICA

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

(Do[If[w*x == 3 y*z, s = s + 1],

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

Map[t[#] &, Range[0, 50]] (* A212020 *)

%/2  (* integers *)

(* Peter J. C. Moses, Apr 13 2012 *)

CROSSREFS

Cf. A211795.

Sequence in context: A072835 A096229 A231718 * A283597 A112277 A078754

Adjacent sequences:  A212017 A212018 A212019 * A212021 A212022 A212023

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 28 2012

STATUS

approved

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Last modified August 21 22:32 EDT 2019. Contains 326169 sequences. (Running on oeis4.)