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A318031
Number of nX2 0..1 arrays with every element unequal to 0, 1, 3 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.
2
2, 3, 6, 11, 22, 46, 91, 182, 371, 746, 1498, 3027, 6102, 12283, 24766, 49926, 100587, 202726, 408611, 823442, 1659506, 3344611, 6740518, 13584427, 27377702, 55175838, 111198651, 224105366, 451652627, 910240506, 1834460106, 3697093427
OFFSET
1,1
COMMENTS
Column 2 of A318037.
LINKS
FORMULA
Empirical: a(n) = a(n-1) +4*a(n-3) +a(n-5) -a(n-6)
EXAMPLE
Some solutions for n=5
..0..0. .0..0. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..0. .0..0
..0..1. .0..0. .0..1. .0..0. .1..0. .0..0. .1..0. .1..0. .0..0. .1..0
..0..0. .0..0. .0..0. .0..0. .1..1. .0..0. .0..0. .0..0. .0..0. .0..0
..0..0. .1..0. .0..0. .1..0. .1..1. .1..0. .0..1. .0..0. .0..0. .0..0
..1..0. .0..0. .0..0. .1..1. .0..1. .0..0. .0..0. .0..0. .1..0. .1..0
CROSSREFS
Cf. A318037.
Sequence in context: A244521 A096202 A036653 * A316500 A123769 A093304
KEYWORD
nonn
AUTHOR
R. H. Hardin, Aug 13 2018
STATUS
approved