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 A209944 Half the number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having at most one duplicate clockwise edge difference. 1
 34, 258, 1956, 14832, 112464, 852768, 6466176, 49030272, 371775744, 2819017728, 21375415296, 162080704512, 1228989210624, 9318903717888, 70661292834816, 535794601623552, 4062703123759104, 30805753962037248, 233586961257332736 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A209951. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 6*a(n-1) + 12*a(n-2). Conjectures from Colin Barker, Jul 14 2018: (Start) G.f.: 2*x*(17 + 27*x) / (1 - 6*x - 12*x^2). a(n) = ((3-sqrt(21))^n*(-41+9*sqrt(21)) + (3+ sqrt(21))^n*(41+9*sqrt(21))) / (4*sqrt(21)). (End) EXAMPLE Some solutions for n=4: ..2..0....0..1....1..1....2..1....2..1....2..1....2..1....2..2....1..2....2..0 ..2..2....2..0....2..0....0..0....0..2....2..2....0..2....1..2....0..2....1..2 ..0..1....1..2....0..1....1..1....1..1....1..2....1..2....2..2....0..2....0..2 ..2..1....2..0....2..2....1..0....1..2....0..2....2..2....1..2....2..2....1..0 ..2..1....0..1....2..1....2..2....1..1....2..2....1..0....1..1....0..2....2..2 CROSSREFS Cf. A209951. Sequence in context: A183319 A190422 A209951 * A081219 A254700 A241698 Adjacent sequences:  A209941 A209942 A209943 * A209945 A209946 A209947 KEYWORD nonn AUTHOR R. H. Hardin, Mar 16 2012 STATUS approved

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Last modified August 11 10:15 EDT 2022. Contains 356065 sequences. (Running on oeis4.)