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%I #5 Aug 12 2016 07:05:19
%S 1,3,20,138,1488,20400,317520,5911920,126080640,2999566080,79604985600
%N Number of nX3 arrays containing 3 copies of 0..n-1 with every element equal to at least one horizontal or vertical neighbor and the top left element equal to 0.
%C Column 3 of A267901.
%e Some solutions for n=4
%e ..0..0..1....0..0..0....0..0..0....0..0..1....0..1..1....0..0..3....0..2..2
%e ..0..1..1....2..3..3....1..1..1....2..0..1....0..1..2....0..3..3....0..0..2
%e ..2..2..3....2..3..1....2..2..2....2..2..1....0..2..2....1..1..1....3..1..1
%e ..2..3..3....2..1..1....3..3..3....3..3..3....3..3..3....2..2..2....3..3..1
%Y Cf. A267901.
%K nonn
%O 1,2
%A _R. H. Hardin_, Jan 22 2016