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%I #6 Dec 18 2015 18:18:07
%S 0,1,9,239,14669,2313041,915560157,915512113455,2309733753013069,
%T 14705975948890342013,236286306641789616616527,
%U 9580759647090339471565196845,980341335177418943590433413869387
%N 1/3 the number of n X n 0..2 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors
%H R. H. Hardin, <a href="/A211052/b211052.txt">Table of n, a(n) for n = 1..14</a>
%e Some solutions for n=4
%e ..0..0..1..0....1..1..2..2....1..1..0..0....2..2..0..2....0..0..1..1
%e ..0..1..1..0....1..1..2..1....1..1..1..1....2..2..0..2....0..0..2..2
%e ..1..1..1..1....2..2..1..1....0..1..1..0....0..0..2..2....1..2..2..2
%e ..0..0..1..1....2..1..1..1....0..1..0..0....2..2..2..2....1..2..2..2
%K nonn
%O 1,3
%A _R. H. Hardin_ Mar 30 2012
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