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A199641
Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.
1
1, 3, 13, 60, 288, 1384, 6628, 31772, 152304, 730036, 3499340, 16773680, 80402532, 385399644, 1847365808, 8855120468, 42445929772, 203459338800, 975257291396, 4674775757500, 22407962058928, 107409807372276, 514855687878924
OFFSET
1,2
COMMENTS
Column 2 of A199647.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) +7*a(n-2) +8*a(n-3) -8*a(n-5) for n>7.
Empirical g.f.: x*(1 - 3*x^2 - 8*x^3 - 7*x^4 + 4*x^5 + 4*x^6) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - Colin Barker, May 16 2018
EXAMPLE
Some solutions for n=3:
..0..1....0..0....0..0....0..1....0..0....0..0....0..0....0..1....0..0....0..0
..0..1....0..0....1..0....0..1....1..1....1..1....1..0....0..1....0..1....0..1
..0..1....1..1....1..0....2..2....1..1....2..2....1..1....1..1....0..1....1..1
CROSSREFS
Cf. A199647.
Sequence in context: A074437 A026578 A362596 * A357151 A367058 A353208
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 08 2011
STATUS
approved