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%I #5 Dec 18 2015 18:18:08
%S 1,10,247,15457,2424088,951410443,932290081063,2278103185689373,
%T 13868101018687422769,210186367992374120026696
%N 1/4 the number of n X n 0..3 symmetric matrices with every element equal to zero, two or three horizontal and vertical neighbors
%e Some solutions for n=4
%e ..3..0..1..3....1..2..0..1....3..0..2..1....1..3..2..0....0..3..3..0
%e ..0..2..3..1....2..1..3..2....0..2..1..2....3..1..3..1....3..3..3..1
%e ..1..3..0..2....0..3..1..0....2..1..0..1....2..3..2..0....3..3..1..2
%e ..3..1..2..0....1..2..0..2....1..2..1..2....0..1..0..3....0..1..2..0
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 31 2012
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