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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
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
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.)