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 A221454 Number of 0..3 arrays of length n with each element unequal to at least one neighbor, with new values introduced in 0..3 order. 2
 0, 1, 2, 7, 24, 88, 328, 1235, 4668, 17675, 66974, 253858, 962352, 3648397, 13831870, 52440191, 198815196, 753764564, 2857736696, 10834499599, 41076702120, 155733594211, 590430871282, 2238493367822, 8486772670944, 32175798041273 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Column 3 of A221459. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 4*a(n-1) + a(n-2) - 6*a(n-3) - 3*a(n-4). Empirical g.f.: x^2*(1 - 2*x - 2*x^2) / ((1 - x - x^2)*(1 - 3*x - 3*x^2)). - Colin Barker, Mar 14 2018 EXAMPLE Some solutions for n=6: ..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0 ..1....1....1....1....1....1....1....1....1....1....1....1....1....1....1....1 ..1....2....2....1....0....2....2....2....1....2....2....2....2....2....2....2 ..0....2....3....2....1....0....1....3....2....1....1....1....3....2....3....0 ..0....1....2....2....2....1....3....3....1....2....2....0....3....0....1....0 ..1....3....1....0....0....3....1....2....2....3....0....3....1....3....2....1 CROSSREFS Cf. A221459. Sequence in context: A227824 A270490 A104625 * A151293 A122446 A150390 Adjacent sequences: A221451 A221452 A221453 * A221455 A221456 A221457 KEYWORD nonn AUTHOR R. H. Hardin, Jan 17 2013 STATUS approved

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Last modified July 14 12:56 EDT 2024. Contains 374318 sequences. (Running on oeis4.)