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 A230835 Number of n X 2 0..3 arrays x(i,j) with each element horizontally, vertically or antidiagonally next to at least one element with value (x(i,j)+1) mod 4, and upper left element zero. 1
 0, 2, 22, 162, 1202, 8974, 66990, 500018, 3732178, 27857358, 207930158, 1552011826, 11584373970, 86466944462, 645398059822, 4817316700722, 35956941366482, 268386264128974, 2003262347565870, 14952553724011058, 111607380401824978 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 8*a(n-1) - 5*a(n-2) + 8*a(n-3) - 4*a(n-4). Empirical g.f.: 2*x^2*(1 + 3*x - 2*x^2) / ((1 + x^2)*(1 - 8*x + 4*x^2)). - Colin Barker, Sep 22 2018 EXAMPLE Some solutions for n=3: ..0..3....0..1....0..0....0..0....0..3....0..1....0..1....0..1....0..1....0..0 ..1..0....2..0....1..0....1..3....1..2....2..3....2..0....3..2....3..2....1..2 ..2..3....3..3....2..3....2..1....1..1....1..0....3..2....1..0....0..1....0..3 CROSSREFS Column 2 of A230840. Sequence in context: A265864 A091169 A279380 * A270407 A000184 A007613 Adjacent sequences:  A230832 A230833 A230834 * A230836 A230837 A230838 KEYWORD nonn AUTHOR R. H. Hardin, Oct 31 2013 STATUS approved

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Last modified January 17 16:43 EST 2019. Contains 319235 sequences. (Running on oeis4.)