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%I #22 May 28 2021 18:37:54
%S 0,0,8,64,292,916,2344,5048,10096,18296,31400,50752,79308,118876,
%T 173768,246096,342256,465064,622904,818552,1063756,1361564,1725432,
%U 2159384,2682944,3298568,4027776,4873600
%N Number of concave kites (darts or arrowheads) on an n X n grid (or geoboard).
%H Nathaniel Johnston, <a href="/A173502/a173502.c.txt">C program for computing terms</a>
%e a(1) = 0, since there is only one point on a 1 X 1 grid.
%e a(2) = 0, since the four points on a 2 X 2 grid build a convex quadrilateral.
%e a(3) = 8, since there are two possible forms of darts on a 3 X 3 grid, each can appear in four rotations.
%Y Cf. A189412, A189417.
%K nonn
%O 1,3
%A _Martin Renner_, Apr 29 2011
%E a(7)-a(28) from _Nathaniel Johnston_, Apr 29 2011
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