A212136 - OEIS

A212136

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

0, 1, 7, 25, 60, 126, 222, 387, 599, 903, 1295, 1830, 2458, 3322, 4317, 5539, 6993, 8773, 10766, 13198, 15906, 19095, 22707, 26879, 31376, 36684, 42500, 49024, 56131, 64205, 72833, 82742, 93314, 104934, 117500, 131277, 146003, 162489

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OFFSET

0,3

COMMENTS

A212136(n)+A212150(n)=n^4. For a guide to related sequences, see A211795.

LINKS

Table of n, a(n) for n=0..37.

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, 40]] (* A212136 *)

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

CROSSREFS

Cf. A211795.

Sequence in context: A266709 A162264 A034135 * A213392 A061600 A098538

Adjacent sequences: A212133 A212134 A212135 * A212137 A212138 A212139

KEYWORD

nonn

AUTHOR

Clark Kimberling, May 07 2012

EXTENSIONS

Offset changed to 0 by Georg Fischer, Feb 02 2022

STATUS

approved