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A199142 Number of n X 1 0..3 arrays with values 0..3 introduced in row major order and each element equal to one or two horizontal and vertical neighbors. 3
0, 1, 1, 2, 3, 6, 11, 23, 47, 102, 221, 492, 1099, 2485, 5637, 12858, 29391, 67354, 154539, 355003, 816035, 1876862, 4318201, 9937840, 22874731, 52659593, 121237417, 279141170, 642732027, 1479959118, 3407837387, 7847200511 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,4
COMMENTS
Column 1 of A199149.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) + a(n-2) - 7*a(n-3) + a(n-4) + 3*a(n-5) for n>6.
Empirical g.f.: x^2*(1 - 2*x - 2*x^2 + 3*x^3 + x^4) / ((1 - x)*(1 - x - x^2)*(1 - x - 3*x^2)). - Colin Barker, Feb 22 2018
EXAMPLE
Some solutions for n=8:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..1....0....0....1....1....1....0....1....1....0....1....0....0....0....1....0
..1....1....0....1....1....1....1....1....1....0....1....0....0....0....1....0
..2....1....1....1....1....0....1....2....1....0....2....1....0....1....1....0
..2....1....1....0....2....0....0....2....1....1....2....1....0....1....1....0
..2....0....0....0....2....1....0....1....0....1....3....1....0....2....2....1
..2....0....0....0....2....1....0....1....0....1....3....1....0....2....2....1
CROSSREFS
Cf. A199149.
Sequence in context: A001190 A274937 A359392 * A090344 A277795 A198662
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 03 2011
STATUS
approved

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Last modified February 23 04:31 EST 2024. Contains 370267 sequences. (Running on oeis4.)