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Number of n X n symmetric 0..4 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 4 and with new values 0..4 introduced in lower triangular row major order
0

%I #5 Dec 18 2015 18:17:41

%S 0,0,0,0,0,21,1640,407889,76204819,26261341398,12631545191076

%N Number of n X n symmetric 0..4 arrays with each element equal to at least two horizontal or vertical neighbors, containing at least one 4 and with new values 0..4 introduced in lower triangular row major order

%e Some solutions for 6X6

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

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

%e ..1..1..2..2..4..4....1..1..2..2..4..4....1..1..2..2..3..3....0..0..1..1..3..3

%e ..1..1..2..2..4..4....1..1..2..2..4..4....1..1..2..2..3..3....0..0..1..1..3..3

%e ..3..3..4..4..3..3....3..3..4..4..1..1....3..3..3..3..4..4....2..2..3..3..4..4

%e ..3..3..4..4..3..3....3..3..4..4..1..1....3..3..3..3..4..4....2..2..3..3..4..4

%K nonn

%O 1,6

%A _R. H. Hardin_ Jul 11 2011