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 A221276 Number of 2Xn arrays of occupancy after each element moves to some horizontal, diagonal or antidiagonal neighbor, with every occupancy equal to zero or two 1
 0, 4, 4, 25, 52, 196, 520, 1681, 4840, 14884, 44044, 133225, 397852, 1196836, 3585040, 10764961, 32278480, 96864964, 290545684, 871725625, 2615029252, 7845353476, 23535617560, 70607649841, 211821620920, 635467254244, 1906397776924 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Row 2 of A221275 LINKS R. H. Hardin, Table of n, a(n) for n = 1..94 FORMULA Empirical: a(n) = 4*a(n-1) -12*a(n-3) +9*a(n-4) EXAMPLE Some solutions for n=4 ..0..0..0..2....0..2..2..0....2..2..2..0....2..0..0..0....0..2..2..0 ..2..2..2..0....2..0..0..2....0..0..0..2....0..2..2..2....0..2..2..0 CROSSREFS Sequence in context: A269152 A269097 A171633 * A117429 A132650 A112953 Adjacent sequences:  A221273 A221274 A221275 * A221277 A221278 A221279 KEYWORD nonn AUTHOR R. H. Hardin Jan 09 2013 STATUS approved

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