|
|
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
|
See A211795 for a guide to related sequences.
|
|
LINKS
|
|
|
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 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|