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%I #7 Dec 27 2023 00:14:39
%S 0,1,0,6,8,118,880,14400,318220,10446298,531060152,39577654480,
%T 4465022457276,757302604610482,191605833481050984
%N 1/3 the number of n X n 0..2 symmetric matrices with every element equal to two or three horizontal and vertical neighbors.
%e Some solutions for n=4
%e ..0..0..1..1....0..0..1..1....2..2..0..0....2..2..1..1....1..1..1..1
%e ..0..0..1..1....0..0..1..1....2..2..0..0....2..2..1..1....1..2..2..1
%e ..1..1..0..0....1..1..2..2....0..0..1..1....1..1..2..2....1..2..2..1
%e ..1..1..0..0....1..1..2..2....0..0..1..1....1..1..2..2....1..1..1..1
%K nonn
%O 1,4
%A _R. H. Hardin_, Mar 30 2012
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