

A173502


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


2



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
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OFFSET

1,3


LINKS

Table of n, a(n) for n=1..28.
Nathaniel Johnston, C program for computing terms


EXAMPLE

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.


CROSSREFS

Cf. A189412, A189417.
Sequence in context: A189265 A167239 A236554 * A223670 A189618 A189690
Adjacent sequences: A173499 A173500 A173501 * A173503 A173504 A173505


KEYWORD

nonn


AUTHOR

Martin Renner, Apr 29 2011


EXTENSIONS

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


STATUS

approved



