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 A209789 Half the number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having exactly one duplicate clockwise edge difference. 1
 30, 204, 1380, 9348, 63300, 428676, 2902980, 19659012, 133130820, 901562244, 6105381060, 41345652228, 279992833860, 1896111996036, 12840473986500, 86955713884932, 588864257262660, 3987789852932484, 27005320351814340 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A209796. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 5*a(n-1) + 12*a(n-2). Conjectures from Colin Barker, Jul 13 2018: (Start) G.f.: 6*x*(5 + 9*x) / (1 - 5*x - 12*x^2). a(n) = (2^(-2-n)*(3*(5+sqrt(73))^n*(25+3*sqrt(73)) + (5-sqrt(73))^n*(-75+9*sqrt(73)))) / sqrt(73). (End) EXAMPLE Some solutions for n=4: ..2..0....1..2....0..1....1..1....2..1....2..1....2..1....0..0....0..2....1..2 ..1..0....0..2....2..1....2..0....1..1....0..0....0..0....2..1....2..2....0..2 ..0..0....2..2....1..1....0..0....0..1....2..0....1..1....2..0....0..1....0..2 ..1..0....2..0....2..0....2..2....2..2....0..0....1..0....1..0....0..1....2..2 ..2..2....0..0....0..0....2..1....1..2....1..0....2..2....0..0....1..1....0..2 CROSSREFS Cf. A209796. Sequence in context: A165030 A165016 A209796 * A280482 A203617 A181629 Adjacent sequences:  A209786 A209787 A209788 * A209790 A209791 A209792 KEYWORD nonn AUTHOR R. H. Hardin, Mar 13 2012 STATUS approved

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Last modified September 25 00:48 EDT 2020. Contains 337333 sequences. (Running on oeis4.)