A173502 Number of concave kites (darts or arrowheads) on an n X n grid (or geoboard).

0, 0, 8, 64, 292, 916, 2344, 5048, 10096, 18296, 31400, 50752, 79308, 118876, 173768, 246096, 342256, 465064, 622904, 818552, 1063756, 1361564, 1725432, 2159384, 2682944, 3298568, 4027776, 4873600

Offset: 1

Author

Martin Renner, Apr 29 2011

Keywords

• nonn

Examples

			a(1) = 0, since there is only one point on a 1 X 1 grid.
a(2) = 0, since the four points on a 2 X 2 grid build a convex quadrilateral.
a(3) = 8, since there are two possible forms of darts on a 3 X 3 grid, each can appear in four rotations.
		

Links

• Nathaniel Johnston, C program for computing terms

Crossrefs

Cf. A189412, A189417.

Extensions

a(7)-a(28) from Nathaniel Johnston, Apr 29 2011