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A212111 Number of (w,x,y,z) with all terms in {1,...,n} and w*x+y*z<n^2. 2
0, 0, 5, 48, 180, 481, 1034, 1986, 3441, 5602, 8623, 12755, 18126, 25165, 33951, 44936, 58367, 74638, 93934, 116987, 143760, 175126, 211253, 252782, 299884, 353673, 414098, 482057, 557997, 642810, 736317, 840479, 954638, 1080451 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

A212111(n)+A212132(n)=n^4.  For a guide to related sequences, see A211795.

LINKS

Table of n, a(n) for n=0..33.

MATHEMATICA

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

(Do[If[w*x + y*z < n^2, s = s + 1],

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

Map[t[#] &, Range[0, 60]]   (* A212111 *)

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

CROSSREFS

Cf. A211795.

Sequence in context: A291863 A247705 A215543 * A215050 A268785 A268736

Adjacent sequences:  A212108 A212109 A212110 * A212112 A212113 A212114

KEYWORD

nonn

AUTHOR

Clark Kimberling, May 07 2012

STATUS

approved

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Last modified October 1 01:28 EDT 2022. Contains 357134 sequences. (Running on oeis4.)