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A189413 Number of convex quadrilaterals on an n X n grid (or geoboard). 9
0, 1, 70, 1038, 7398, 35727, 130768, 400116, 1062016, 2531001, 5529310, 11272710, 21639022, 39559591, 69283632, 116910052, 190977408, 303286461, 469431366, 710400658, 1053055398, 1532253131 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..22.

Nathaniel Johnston, C program for computing terms

Weisstein, Eric W.: MathWorld -- Convex Polygon.

Weisstein, Eric W.: MathWorld -- Quadrilateral.

CROSSREFS

Cf. A175383, A189345, A189412, A189414.

Sequence in context: A061170 A125114 A281649 * A229735 A254472 A061606

Adjacent sequences:  A189410 A189411 A189412 * A189414 A189415 A189416

KEYWORD

nonn

AUTHOR

Martin Renner, Apr 21 2011

EXTENSIONS

a(6) - a(22) from Nathaniel Johnston, Apr 25 2011

STATUS

approved

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Last modified November 12 16:50 EST 2018. Contains 317116 sequences. (Running on oeis4.)