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

%I #6 Aug 12 2016 06:53:59

%S 1,1,1,1,1,7,41,209,999,4603,20763,92601,410279,1811327,7982401,

%T 35151819,154779159,681698115,3003887511,13244742603,58438985851,

%U 258033686801,1140171589651,5041775026879,22310625017943,98798039343423

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

%C Row 3 of A266886.

%H R. H. Hardin, <a href="/A266887/b266887.txt">Table of n, a(n) for n = 1..88</a>

%e Some solutions for n=7

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

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

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

%Y Cf. A266886.

%K nonn

%O 1,6

%A _R. H. Hardin_, Jan 05 2016