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%I #6 Apr 23 2021 09:41:17
%S 0,0,20,23,1655,39597,336788,2130707,97253704,2328983293,27777628803,
%T 109663812046,7330508486557,181851333483598,2032109646360324,
%U 8979878533633165,588003317861300327
%N Number of n X 3 0..3 arrays with values 0..3 introduced in row major order, the number of instances of each value within one of each other, and every element equal to one or two horizontal or vertical neighbors.
%C Column 3 of A199363.
%e Some solutions for n=4
%e ..0..0..1....0..0..1....0..0..0....0..0..0....0..0..0....0..1..1....0..0..0
%e ..0..1..1....2..0..1....1..2..2....1..2..2....1..1..1....0..0..1....1..2..2
%e ..2..2..2....2..3..1....1..3..2....1..2..3....2..2..3....2..2..3....1..1..2
%e ..3..3..3....2..3..3....1..3..3....1..3..3....2..3..3....2..3..3....3..3..3
%Y Cf. A199363.
%K nonn
%O 1,3
%A _R. H. Hardin_ Nov 05 2011