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Number of 3Xn arrays containing n copies of 0..3-1 with no element 1 greater than its west or southwest neighbor modulo 3 and the upper left element equal to 0.
2

%I #6 Aug 12 2016 06:54:00

%S 2,2,6,31,141,550,2046,8149,34902,152001,652150,2761689,11707811,

%T 50123854,216480177,938377955,4069585995,17658916102,76776575711,

%U 334729181549,1462999055814,6405806909581,28085236208039,123289001886325

%N Number of 3Xn arrays containing n copies of 0..3-1 with no element 1 greater than its west or southwest neighbor modulo 3 and the upper left element equal to 0.

%C Row 3 of A267072.

%H R. H. Hardin, <a href="/A267073/b267073.txt">Table of n, a(n) for n = 1..93</a>

%e Some solutions for n=4

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

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

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

%Y Cf. A267072.

%K nonn

%O 1,1

%A _R. H. Hardin_, Jan 10 2016