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%I #6 Aug 12 2016 06:53:59
%S 2,5,15,109,574,2840,13767,71646,390862,2170370,11989812,66094738,
%T 366119221,2044786962,11503587136,65003352026,368281990242,
%U 2091514533360,11909843102866,68009104297282,389348569168108,2233795881384252
%N Number of 3Xn arrays containing n copies of 0..3-1 with no element 1 greater than its northwest or southwest neighbor modulo 3 and the upper left element equal to 0.
%C Row 3 of A266572.
%H R. H. Hardin, <a href="/A266573/b266573.txt">Table of n, a(n) for n = 1..73</a>
%e Some solutions for n=6
%e ..0..1..1..0..0..1....0..2..0..1..1..0....0..2..2..0..1..2....0..1..0..0..1..1
%e ..2..2..0..1..2..0....2..0..1..2..0..1....2..0..1..2..0..1....2..0..0..2..2..0
%e ..2..1..2..0..1..2....0..1..2..1..2..2....1..1..0..1..2..0....1..1..2..2..1..2
%Y Cf. A266572.
%K nonn
%O 1,1
%A _R. H. Hardin_, Jan 01 2016
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