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A267903
Number of 3Xn arrays containing n copies of 0..3-1 with every element equal to at least one horizontal or vertical neighbor and the top left element equal to 0.
1
0, 6, 20, 268, 2324, 28318, 315196, 3786836, 45099306, 547824556, 6687936028, 82350672500, 1019550923830, 12691867518330, 158695413996448, 1992293553570646, 25099547132728742, 317210539882144928
OFFSET
1,2
COMMENTS
Row 3 of A267901.
LINKS
EXAMPLE
Some solutions for n=4
..0..2..1..1....0..0..2..2....0..0..1..1....0..2..2..1....0..0..1..1
..0..2..0..2....2..2..1..0....2..1..1..0....0..0..0..1....2..0..1..1
..1..1..0..2....1..1..1..0....2..2..2..0....1..1..2..2....2..0..2..2
CROSSREFS
Cf. A267901.
Sequence in context: A347919 A227769 A309454 * A330825 A280039 A216912
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 22 2016
STATUS
approved