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 A198662 Number of n X 1 0..4 arrays with values 0..4 introduced in row major order and each element equal to one or two horizontal and vertical neighbors. 2
 0, 1, 1, 2, 3, 6, 11, 23, 47, 103, 226, 517, 1194, 2830, 6778, 16498, 40501, 100420, 250513, 628749, 1584525, 4007957, 10164528, 25835883, 65777232, 167694004, 427960360, 1093068944, 2793604179, 7143313914, 18272673575, 46755936515 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS Column 1 of A198669. LINKS R. H. Hardin, Table of n, a(n) for n = 1..200 FORMULA Empirical: a(n) = 4*a(n-1) + a(n-2) - 17*a(n-3) + 6*a(n-4) + 21*a(n-5) - 6*a(n-6) - 8*a(n-7) for n>8. Empirical g.f.: x^2*(1 - 3*x^2 - x^3)*(1 - 3*x + 3*x^3) / ((1 - x)*(1 + x)*(1 - 2*x)*(1 - x - x^2)*(1 - x - 4*x^2)). - Colin Barker, Mar 02 2018 EXAMPLE All solutions for n=5: ..0....0....0 ..0....0....0 ..1....0....0 ..1....0....1 ..1....0....1 CROSSREFS Cf. A198669. Sequence in context: A199142 A090344 A277795 * A198620 A198648 A198655 Adjacent sequences:  A198659 A198660 A198661 * A198663 A198664 A198665 KEYWORD nonn AUTHOR R. H. Hardin, Oct 28 2011 STATUS approved

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Last modified December 2 23:22 EST 2021. Contains 349445 sequences. (Running on oeis4.)