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A189414 Number of quadrilaterals on an (n X n)-grid (or geoboard). 6
0, 1, 94, 1758, 13698, 70539, 266320, 837060, 2260984, 5460657, 12046294, 24775158, 47847538, 87967579, 154764912, 262110940, 429480216, 684015621, 1061192670, 1609449754, 2390049498, 3483126407 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

Weisstein, Eric W.: MathWorld -- Quadrilateral.

FORMULA

a(n) = A189412(n) + A189413(n).

CROSSREFS

Cf. A175383, A189345, A189412, A189413.

Sequence in context: A220961 A218648 A278321 * A195757 A017810 A035742

Adjacent sequences:  A189411 A189412 A189413 * A189415 A189416 A189417

KEYWORD

nonn

AUTHOR

Martin Renner, Apr 21 2011

EXTENSIONS

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

a(7) - a(22) corrected by Michal Forisek, Sep 06 2011

STATUS

approved

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Last modified December 16 07:12 EST 2018. Contains 318158 sequences. (Running on oeis4.)