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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 R. H. Hardin, Table of n, a(n) for n = 1..210 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 Adjacent sequences: A202970 A202971 A202972 * A202974 A202975 A202976 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.)