OFFSET
0,2
LINKS
Vincenzo Librandi and Chai Wah Wu, Table of n, a(n) for n = 0..10000 (terms for n = 0..100 from Vincenzo Librandi)
FORMULA
a(n) = A134506(n) + (2n+1)^2. Shi's result (see formula section in A134506) shows that a(n) = kn^2 log n + cn^2 + O(n^e) where k = 12/Pi^2, e > 547/416 = 1.3149..., and c = 4.5113... - Chai Wah Wu, Nov 28 2016
MATHEMATICA
a[0] = 1; a[n_] := Table[{w, x, y, z} /. {ToRules[ Reduce[0 <= x <= n && 0 <= y <= n && 0 <= z <= n && w*z - x*y == 0, {x, y, z}, Integers]] }, {w, 0, n}] // Flatten[#, 1]& // Length; Table[Print[an = a[n]]; an, {n, 0, 42}] (* Jean-François Alcover, Oct 11 2013 *)
CROSSREFS
KEYWORD
nonn,nice
AUTHOR
John W. Layman, Jan 25 2001
EXTENSIONS
More terms from Larry Reeves (larryr(AT)acm.org), Jan 09 2003
STATUS
approved