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A221256
Number of 2 X n arrays of occupancy after each element moves to some horizontal or antidiagonal neighbor, with no occupancy greater than 2.
1
0, 4, 8, 81, 392, 2500, 14112, 83521, 484128, 2829124, 16473800, 96059601, 559785800, 3262922884, 19017180288, 110841719041, 646029804672, 3765346202500, 21946028005832, 127910874833361, 745519107896648
OFFSET
1,2
COMMENTS
Row 2 of A221255.
LINKS
FORMULA
Empirical: a(n) = 6*a(n-1) + 6*a(n-2) - 42*a(n-3) + 42*a(n-5) - 6*a(n-6) - 6*a(n-7) + a(n-8).
Empirical g.f.: x^2*(4 - 16*x + 9*x^2 + 26*x^3 - 2*x^4 - 6*x^5 + x^6) / ((1 - x)*(1 + x)*(1 - 6*x + x^2)*(1 + 2*x - x^2)*(1 - 2*x - x^2)). - Colin Barker, Aug 04 2018
EXAMPLE
Some solutions for n=3:
0 2 2 1 2 0 0 2 1 0 2 1 0 2 0 1 2 0 1 2 1
0 2 0 0 2 1 0 2 1 1 2 0 1 2 1 1 2 0 0 2 0
CROSSREFS
Cf. A221255.
Sequence in context: A353032 A236284 A276979 * A068208 A090254 A222287
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 06 2013
STATUS
approved