A189414 Number of quadrilaterals on an n X n grid (or geoboard).

0, 1, 94, 1758, 13698, 70539, 266320, 837060, 2260984, 5460657, 12046294, 24775158, 47847538, 87967579, 154764912, 262110940, 429480216, 684015621, 1061192670, 1609449754, 2390049498, 3483126407

Offset

1,3

Links

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

Eric Weisstein's World of Mathematics, Quadrilateral.

Formula

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

Crossrefs

Cf. A175383, A189345, A189412, A189413.

Sequence in context: A220961 A218648 A278321 * A339143 A370237 A347723

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