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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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 2 of A199647. LINKS R. H. Hardin, Table of n, a(n) for n = 1..200 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: A340411 A074437 A026578 * A340412 A340413 A340414 Adjacent sequences:  A199638 A199639 A199640 * A199642 A199643 A199644 KEYWORD nonn AUTHOR R. H. Hardin, Nov 08 2011 STATUS approved

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Last modified July 30 21:33 EDT 2021. Contains 346365 sequences. (Running on oeis4.)