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 A251328 Number of (n+1) X (1+1) 0..2 arrays with every 2 X 2 subblock summing to 2 4 or 6. 1
 39, 171, 753, 3333, 14823, 66219, 297057, 1337733, 6045495, 27408747, 124625745, 568146309, 2596130823, 11887635627, 54533628609, 250576195845, 1153020767319, 5312272049259, 24501992068785, 113120150702085, 522688044131367 (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) = 8*a(n-1) - 13*a(n-2) - 12*a(n-3). Conjectures from Colin Barker, Nov 29 2018: (Start) G.f.: 3*x*(13 - 47*x - 36*x^2) / ((1 - 4*x)*(1 - 4*x - 3*x^2)). a(n) = (7*2^(3+2*n) + (35-13*sqrt(7))*(2-sqrt(7))^n + (2+sqrt(7))^n*(35+13*sqrt(7))) / 14. (End) EXAMPLE Some solutions for n=4: ..2..0....2..0....2..1....0..1....1..2....1..1....2..0....2..2....2..0....0..0 ..1..1....0..2....2..1....2..1....0..1....1..1....1..1....0..2....1..1....2..0 ..1..1....0..0....1..0....0..1....1..0....1..1....0..2....2..0....1..1....2..2 ..0..0....1..1....1..2....1..2....2..1....0..2....0..2....0..2....0..0....1..1 ..2..2....0..2....1..2....1..2....1..2....0..2....2..2....2..0....1..1....0..0 CROSSREFS Column 1 of A251335. Sequence in context: A158598 A105838 A251335 * A235981 A235974 A258095 Adjacent sequences:  A251325 A251326 A251327 * A251329 A251330 A251331 KEYWORD nonn AUTHOR R. H. Hardin, Dec 01 2014 STATUS approved

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Last modified March 20 15:43 EDT 2019. Contains 321345 sequences. (Running on oeis4.)