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A212517 Number of (w,x,y,z) with all terms in {1,...,n} and w>2x and y<=3z. 2
0, 0, 0, 9, 30, 92, 198, 396, 684, 1152, 1760, 2650, 3780, 5292, 7140, 9555, 12376, 15936, 20088, 25110, 30870, 37800, 45540, 54692, 64944, 76752, 89856, 104949, 121394, 140140, 160650, 183600, 208560, 236544, 266560, 299982, 335988 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

For a guide to related sequences, see A211795.

LINKS

Table of n, a(n) for n=0..36.

FORMULA

a(n)=2a(n-2)+2a(n-3)-a(n-4)-4a(n-5)+2a(n-7)-2a(n-9)+4a(n-11)+ a(n-12)-2a(n-13)-2a(n-14)+a(n-16).

MATHEMATICA

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

(Do[If[w > 2 x && y <= 3 z, s = s + 1],

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

Map[t[#] &, Range[0, 50]]   (* A212517 *)

FindLinearRecurrence[%]

CROSSREFS

Cf. A211795, A212508.

Sequence in context: A084370 A000439 A002414 * A000440 A161684 A054310

Adjacent sequences:  A212514 A212515 A212516 * A212518 A212519 A212520

KEYWORD

nonn

AUTHOR

Clark Kimberling, May 20 2012

STATUS

approved

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Last modified October 23 03:24 EDT 2014. Contains 248411 sequences.