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Number of n X n 0..2 arrays with values 0..2 introduced in row major order, the number of instances of each value within one of each other, and every element equal to zero or two horizontal or vertical neighbors
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%I #6 Dec 18 2015 18:17:54

%S 1,2,6,440,29227,1682457,2013526831

%N Number of n X n 0..2 arrays with values 0..2 introduced in row major order, the number of instances of each value within one of each other, and every element equal to zero or two horizontal or vertical neighbors

%C Diagonal of A199246

%e Some solutions for n=4

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

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

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

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

%K nonn

%O 1,2

%A _R. H. Hardin_ Nov 04 2011