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 A220997 Number of n X 2 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor. 3
 3, 31, 306, 2989, 29135, 283872, 2765627, 26943707, 262494146, 2557299561, 24914003827, 242719929760, 2364652602239, 23037176752223, 224435298485050, 2186518067974709, 21301735038155095, 207528088736659200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 2 of A221001. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 11*a(n-1) - 11*a(n-2) - 12*a(n-3) - 2*a(n-4). Empirical g.f.: x*(3 - 2*x - 2*x^2) / (1 - 11*x + 11*x^2 + 12*x^3 + 2*x^4). - Colin Barker, Feb 23 2018 EXAMPLE Some solutions for n=3: ..2..1....3..0....1..1....0..2....0..2....0..1....1..1....3..0....0..1....0..1 ..1..2....0..1....1..1....1..1....1..3....2..0....3..0....0..1....1..3....3..1 ..0..0....1..1....0..2....1..1....0..0....1..2....1..0....2..0....0..1....1..0 CROSSREFS Cf. A221001. Sequence in context: A112425 A144579 A348709 * A222094 A069589 A222090 Adjacent sequences: A220994 A220995 A220996 * A220998 A220999 A221000 KEYWORD nonn AUTHOR R. H. Hardin, Dec 28 2012 STATUS approved

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Last modified March 29 07:53 EDT 2023. Contains 361596 sequences. (Running on oeis4.)