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 A262415 Number of (n+1) X (3+1) 0..1 arrays with each row divisible by 3 and column not divisible by 3, read as a binary number with top and left being the most significant bits. 1
 6, 45, 270, 1701, 10206, 61965, 371790, 2237301, 13423806, 80601885, 483611310, 2902199301, 17413195806, 104483957805, 626903746830, 3761465527701, 22568793166206, 135413146417725, 812478878506350, 4874876757822501 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 6*a(n-1) + 9*a(n-2) - 54*a(n-3). Conjectures from Colin Barker, Dec 31 2018: (Start) G.f.: 3*x*(2 + 3*x - 18*x^2) /  ((1 - 3*x)*(1 + 3*x)*(1 - 6*x)). a(n) = 3^(n-1) * (2^(n+3) - 2) / 2 for n even. a(n) = 3^(n-1) * (2^(n+3) - 4) / 2 for n odd. (End) EXAMPLE Some solutions for n=4: ..0..0..1..1....1..1..1..1....1..1..1..1....1..1..0..0....1..1..0..0 ..0..0..0..0....0..0..1..1....0..0..0..0....0..0..1..1....1..1..0..0 ..1..1..0..0....1..0..0..1....1..0..0..1....0..0..1..1....1..1..0..0 ..0..0..1..1....1..1..0..0....0..0..0..0....0..0..1..1....0..0..1..1 ..0..0..1..1....0..1..1..0....0..1..1..0....0..0..0..0....0..0..0..0 CROSSREFS Column 3 of A262420. Sequence in context: A258350 A258623 A003486 * A297645 A201191 A214982 Adjacent sequences:  A262412 A262413 A262414 * A262416 A262417 A262418 KEYWORD nonn AUTHOR R. H. Hardin, Sep 22 2015 STATUS approved

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Last modified August 7 19:57 EDT 2020. Contains 336279 sequences. (Running on oeis4.)