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A202973 Number of n X 2 0..1 arrays with every nonzero element less than or equal to at least two horizontal and vertical neighbors. 5
1, 2, 4, 7, 14, 31, 69, 155, 354, 814, 1875, 4326, 9993, 23095, 53387, 123430, 285394, 659913, 1525942, 3528541, 8159347, 18867623, 43629460, 100888804, 233295503, 539473228, 1247479743, 2884676711, 6670537293, 15424975984, 35668774074 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Column 2 of A202979.
LINKS
FORMULA
Empirical: a(n) = 3*a(n-1) - 2*a(n-2) + 2*a(n-3) - 2*a(n-4) - a(n-5).
Empirical g.f.: x*(1 - x - 3*x^3 - x^4) / (1 - 3*x + 2*x^2 - 2*x^3 + 2*x^4 + x^5). - Colin Barker, Feb 19 2018
EXAMPLE
Some solutions for n=5:
..0..0....0..0....1..1....0..0....1..1....0..0....1..1....1..1....1..1....1..1
..0..0....1..1....1..1....1..1....1..1....0..0....1..1....1..1....1..1....1..1
..0..0....1..1....0..0....1..1....0..0....0..0....1..1....1..1....1..0....0..1
..1..1....0..0....1..1....1..1....0..0....0..0....0..0....1..1....1..1....1..1
..1..1....0..0....1..1....0..0....0..0....0..0....0..0....1..1....1..1....1..1
CROSSREFS
Sequence in context: A202842 A364589 A013326 * A074663 A325303 A356781
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 26 2011
STATUS
approved

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Last modified April 18 22:18 EDT 2024. Contains 371782 sequences. (Running on oeis4.)