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Number of n X n symmetric 0..3 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 3 and with new values 0..3 introduced in lower triangular row major order
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%I #5 Dec 18 2015 18:17:40

%S 0,0,0,0,0,145,6944,635377,69009813,12541320254,3495358855982,

%T 1626847265319815,1240274531663638765

%N Number of n X n symmetric 0..3 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 3 and with new values 0..3 introduced in lower triangular row major order

%e Some solutions for 6X6

%e ..0..0..0..0..0..0....0..0..1..1..3..3....0..0..1..1..2..2....0..0..0..0..2..2

%e ..0..0..1..1..0..0....0..0..1..1..3..3....0..0..1..1..2..2....0..0..0..0..2..2

%e ..0..1..1..1..2..2....1..1..2..2..3..3....1..1..1..1..1..1....0..0..0..1..1..1

%e ..0..1..1..2..2..2....1..1..2..2..3..3....1..1..1..1..1..1....0..0..1..1..1..1

%e ..0..0..2..2..3..3....3..3..3..3..3..3....2..2..1..1..3..3....2..2..1..1..3..3

%e ..0..0..2..2..3..3....3..3..3..3..3..3....2..2..1..1..3..3....2..2..1..1..3..3

%K nonn

%O 1,6

%A _R. H. Hardin_ Jul 11 2011