A212021 - OEIS

A212021

Number of (w,x,y,z) with all terms in {1,...,n} and 2w*x=3*y*z.

0, 0, 0, 8, 16, 20, 48, 56, 80, 132, 164, 176, 272, 288, 332, 436, 512, 532, 696, 720, 844, 1000, 1076, 1104, 1360, 1430, 1518, 1758, 1942, 1978, 2328, 2368, 2566, 2818, 2938, 3098, 3600, 3648, 3780, 4084, 4440, 4492, 4996, 5052, 5348, 5920

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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[2 w*x == 3 y*z, s = s + 1],

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

Map[t[#] &, Range[0, 50]] (* A212021 *)

%/2 (* integers *)

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

CROSSREFS

Cf. A211795.

Sequence in context: A114435 A327092 A112679 * A096912 A254141 A188438

Adjacent sequences: A212018 A212019 A212020 * A212022 A212023 A212024

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 28 2012

STATUS

approved