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%I #5 Mar 31 2012 12:37:30
%S 258,4975,95794,1845126,35537484,684469520,13183187396,253914272972,
%T 4890505660356,94193393412380,1814208180084540,34942486067121236,
%U 673008393916430500,12962452003109036652,249662802833380927452
%N Half the number of (n+1)X3 0..2 arrays with every 2X2 subblock having at most one duplicate clockwise edge difference
%C Column 2 of A209951
%H R. H. Hardin, <a href="/A209945/b209945.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 20*a(n-1) +25*a(n-2) -708*a(n-3) -1034*a(n-4) +2172*a(n-5) -160*a(n-6) -320*a(n-7)
%e Some solutions for n=4
%e ..0..2..0....2..1..0....0..0..2....0..0..2....1..2..0....1..0..2....1..1..1
%e ..0..1..1....2..1..2....0..1..0....0..1..0....0..2..0....0..2..1....1..0..0
%e ..1..1..2....2..1..1....0..1..1....1..1..0....2..1..1....0..0..2....1..2..2
%e ..2..2..2....0..1..2....0..0..1....1..2..2....2..0..1....1..0..0....0..0..0
%e ..0..1..1....0..0..2....0..2..2....0..0..1....0..0..2....2..0..1....2..0..2
%K nonn
%O 1,1
%A _R. H. Hardin_ Mar 16 2012
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