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%I #6 Mar 31 2012 12:36:34
%S 4,43,658,11029,189376,3272959,56665678,981535273,17003856124,
%T 294580477651,5103458162314,88415060881213,1531751228239288,
%U 26536907089886119,459740106490112326,7964792868501695569
%N Number of 2nX2 0..3 arrays with values 0..3 introduced in row major order and each element unequal to exactly two horizontal and vertical neighbors
%C Column 1 of A198209
%H R. H. Hardin, <a href="/A198205/b198205.txt">Table of n, a(n) for n = 1..200</a>
%F Empirical: a(n) = 23*a(n-1) -103*a(n-2) +81*a(n-3)
%e Some solutions for n=3
%e ..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
%e ..2..2....2..3....2..2....2..0....1..2....2..2....2..2....2..3....2..0....2..2
%e ..1..1....2..3....1..1....2..0....1..2....0..0....3..3....2..3....2..0....0..1
%e ..0..0....3..1....0..2....0..3....0..1....3..2....2..2....0..2....0..3....0..1
%e ..1..1....3..1....0..2....0..3....0..1....3..2....1..1....0..2....0..3....2..2
%e ..3..2....2..3....3..0....3..1....1..3....0..1....3..0....1..0....3..0....1..0
%K nonn
%O 1,1
%A _R. H. Hardin_ Oct 22 2011
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