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 A209906 Half the number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock having two or four distinct clockwise edge differences. 1
 62, 562, 5008, 44770, 399930, 3573388, 31926146, 285247762, 2548561164, 22770302450, 203442764450, 1817673135676, 16240122477074, 145098465897778, 1296391988417932, 11582701309989362, 103486422895200258 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A209913. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 7*a(n-1) + 21*a(n-2) - 30*a(n-3) - 30*a(n-4) + 12*a(n-5) + 8*a(n-6). Empirical g.f.: 2*x*(31 + 64*x - 114*x^2 - 114*x^3 + 46*x^4 + 32*x^5) / (1 - 7*x - 21*x^2 + 30*x^3 + 30*x^4 - 12*x^5 - 8*x^6). - Colin Barker, Jul 13 2018 EXAMPLE Some solutions for n=4: ..0..2....1..2....0..2....2..0....0..0....0..0....3..0....2..0....2..3....1..0 ..0..3....0..3....3..3....2..3....1..3....2..3....1..0....3..0....0..1....0..1 ..0..1....2..2....0..1....1..2....2..1....3..2....0..3....2..0....2..0....0..3 ..2..3....0..3....2..3....0..1....3..2....0..1....2..3....3..1....0..1....1..2 ..1..2....2..2....2..0....1..2....0..3....0..3....1..2....1..2....3..0....2..1 CROSSREFS Cf. A209913. Sequence in context: A212834 A202959 A209913 * A069473 A249530 A249531 Adjacent sequences:  A209903 A209904 A209905 * A209907 A209908 A209909 KEYWORD nonn AUTHOR R. H. Hardin, Mar 15 2012 STATUS approved

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Last modified January 16 02:06 EST 2022. Contains 350374 sequences. (Running on oeis4.)