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Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, with every occupancy equal to zero or two
1

%I #5 Jan 15 2013 20:05:19

%S 0,10,0,150,0,2250,0,33750,0,506250,0,7593750,0,113906250,0,

%T 1708593750,0,25628906250,0,384433593750,0,5766503906250,0,

%U 86497558593750,0,1297463378906250,0,19461950683593750,0,291929260253906250,0

%N Number of nX3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, with every occupancy equal to zero or two

%C Column 3 of A221419

%H R. H. Hardin, <a href="/A221414/b221414.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 15*a(n-2)

%e Some solutions for n=4

%e ..0..2..0....2..2..0....0..2..2....2..0..0....2..2..0....2..0..0....0..2..2

%e ..2..2..0....0..2..0....0..2..0....0..2..2....0..0..2....0..2..0....0..2..0

%e ..2..2..0....2..0..2....0..2..0....2..0..0....2..0..0....2..2..0....2..0..0

%e ..0..0..2....0..2..0....2..2..0....0..2..2....2..2..0....2..2..0....2..2..0

%K nonn

%O 1,2

%A _R. H. Hardin_ Jan 15 2013