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%I #6 Dec 18 2015 18:18:05
%S 1,2,20,400,16716,1444348,258951340,96266852004,74214689922928,
%T 118642250445743920,393305989512539553728,2703723885515478100466476,
%U 38542035415959856159523945096
%N Number of n X n 0..2 symmetric matrices with every element equal to zero or one horizontal and vertical neighbors, and new values 0..2 introduced in lower triangle row major order
%e Some solutions for n=3
%e ..0..1..0....0..1..1....0..1..0....0..1..0....0..1..0....0..1..0....0..1..0
%e ..1..2..0....1..0..2....1..0..2....1..2..1....1..0..1....1..0..2....1..2..0
%e ..0..0..1....1..2..0....0..2..1....0..1..0....0..1..0....0..2..0....0..0..2
%K nonn
%O 1,2
%A _R. H. Hardin_ Mar 29 2012
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