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%I #8 May 03 2018 07:02:34
%S 28,94,200,342,524,732,972,1236,1524,1840,2180,2544,2932,3344,3780,
%T 4240,4724,5232,5764,6320,6900,7504,8132,8784,9460,10160,10884,11632,
%U 12404,13200,14020,14864,15732,16624,17540,18480,19444,20432,21444,22480,23540
%N Number of right triangles on a (n+1) X 4 grid.
%C Column 3 of A189814.
%H R. H. Hardin, <a href="/A189808/b189808.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 12*n^2 + 88*n - 240 for n>8.
%F Conjectures from _Colin Barker_, May 03 2018: (Start)
%F G.f.: 2*x*(14 + 5*x + x^2 - 2*x^3 + 2*x^4 - 7*x^5 + 3*x^6 - 4*x^7 + 2*x^9 - 2*x^10) / (1 - x)^3.
%F a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n>8.
%F (End)
%e Some solutions for n=3:
%e ..3..1....2..2....0..0....2..1....2..0....3..3....1..1....1..1....3..2....1..1
%e ..0..1....3..1....0..3....2..2....0..0....0..3....1..2....0..2....2..2....2..0
%e ..3..2....3..3....2..0....4..1....2..3....3..0....4..1....3..3....3..3....3..3
%Y Cf. A189814.
%K nonn
%O 1,1
%A _R. H. Hardin_, Apr 28 2011
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