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Number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order
1

%I #5 Dec 18 2015 18:18:06

%S 0,1,4,95,9220,3055073,3000338892,8812917082915,76878364475257062,

%T 1995945343880703817038,154116672749530867319434810

%N Number of n X n 0..3 symmetric matrices with every element equal to one, two or three horizontal and vertical neighbors, and new values 0..3 introduced in lower triangle row major order

%e Some solutions for n=4

%e ..0..0..1..0....0..0..1..1....0..0..0..1....0..0..0..0....0..0..1..1

%e ..0..0..1..0....0..0..1..1....0..1..1..1....0..1..1..0....0..0..1..0

%e ..1..1..2..2....1..1..1..0....0..1..1..0....0..1..1..0....1..1..1..0

%e ..0..0..2..2....1..1..0..0....1..1..0..0....0..0..0..0....1..0..0..0

%K nonn

%O 1,3

%A _R. H. Hardin_ Mar 29 2012