login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A211809 Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x>=2*y*z. 2
0, 0, 5, 23, 79, 188, 402, 742, 1283, 2059, 3164, 4633, 6615, 9112, 12299, 16253, 21114, 26924, 33932, 42161, 51885, 63153, 76182, 91068, 108172, 127453, 149257, 173726, 201163, 231591, 265520, 302889, 344195, 389508, 439180, 493458 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n)+A211795(n)=n^4.

See A211795 for a guide to related sequences.

LINKS

Bo Gyu Jeong, Table of n, a(n) for n = 0..200

MATHEMATICA

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

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

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

Map[t[#] &, Range[0, 40]] (* A211809 *)

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

CROSSREFS

Cf. A211795.

Sequence in context: A225266 A293426 A267202 * A211922 A139209 A227123

Adjacent sequences:  A211806 A211807 A211808 * A211810 A211811 A211812

KEYWORD

nonn

AUTHOR

Clark Kimberling, Apr 27 2012

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 19:21 EDT 2020. Contains 333103 sequences. (Running on oeis4.)