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Number of n X n symmetric 0..2 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 2 and with new values 0..2 introduced in lower triangular row major order
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%I #5 Dec 18 2015 18:17:40

%S 0,0,0,1,11,346,8731,349401,20156718,1851292543,266585533037,

%T 61535828576431,22709782832888746,13463873321548595944,

%U 12814751672955863921345

%N Number of n X n symmetric 0..2 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 2 and with new values 0..2 introduced in lower triangular row major order

%e Some solutions for 6X6

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

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

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

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

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

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

%K nonn

%O 1,5

%A _R. H. Hardin_ Jul 11 2011