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A173502 Number of concave kites (darts or arrowheads) on a (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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified November 16 05:13 EST 2018. Contains 317257 sequences. (Running on oeis4.)