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 A206661 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases in its adjacent leftward and upward neighbors. 1
 81, 423, 2286, 12477, 68253, 373644, 2046027, 11205045, 61367382, 336102549, 1840818345, 10082134260, 55219849119, 302439528345, 1656464709102, 9072479040225, 49690095904605, 272153381274660, 1490588111370819 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A206668. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 9*a(n-1) - 18*a(n-2) - 19*a(n-3) + 71*a(n-4) - 28*a(n-5) - 22*a(n-6) + 8*a(n-7). Empirical g.f.: 3*x*(27 - 102*x - 21*x^2 + 352*x^3 - 202*x^4 - 126*x^5 + 56*x^6) / ((1 - x)*(1 - 8*x + 10*x^2 + 29*x^3 - 42*x^4 - 14*x^5 + 8*x^6)). - Colin Barker, Jun 17 2018 EXAMPLE Some solutions for n=4: ..2..0....1..2....1..2....1..2....2..1....1..1....0..1....0..2....2..2....0..2 ..1..2....0..2....2..1....0..1....0..2....2..0....2..0....2..0....1..2....1..1 ..0..2....0..2....0..2....2..1....2..0....0..1....1..2....0..1....2..2....0..2 ..1..1....2..2....2..0....2..2....0..2....2..2....2..0....0..2....1..2....2..2 ..0..2....0..2....0..1....0..0....1..0....2..1....0..1....1..2....1..1....1..1 CROSSREFS Cf. A206668. Sequence in context: A238180 A206414 A205979 * A238173 A206407 A236610 Adjacent sequences: A206658 A206659 A206660 * A206662 A206663 A206664 KEYWORD nonn AUTHOR R. H. Hardin, Feb 11 2012 STATUS approved

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Last modified August 12 19:26 EDT 2024. Contains 375113 sequences. (Running on oeis4.)