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 A204078 Number of nX2 0..3 arrays with every element neighboring horizontally or vertically both a 0 and a 1. 1
 0, 4, 4, 16, 100, 324, 1296, 5476, 21316, 85264, 343396, 1368900, 5475600, 21921124, 87647044, 350588176, 1402502500, 5609710404, 22438841616, 89756564836, 359023862596, 1436095450384, 5744391388516, 22977546380100, 91910185520400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Column 2 of A204084. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 2*a(n-1) +4*a(n-2) +17*a(n-3) -2*a(n-4) -4*a(n-5) -16*a(n-6) Empirical: a(n) = 4*round(2^n/7)^2 - Mark van Hoeij, May 14 2013 Empirical g.f.: 4*x^2*(1 - x - 2*x^2 - 4*x^3) / ((1 - x)*(1 - 4*x)*(1 + x + x^2)*(1 + 2*x + 4*x^2)). - Colin Barker, Jun 06 2018 EXAMPLE Some solutions for n=5: ..0..1....0..0....1..0....1..1....0..0....1..0....0..0....1..0....1..0....0..0 ..0..1....1..1....1..0....0..0....1..1....1..0....1..1....1..0....1..0....1..1 ..2..1....2..2....0..3....1..0....1..1....1..0....1..1....1..0....3..3....0..2 ..1..0....0..0....0..1....1..0....0..0....0..0....0..0....0..0....0..1....0..0 ..1..0....1..1....0..1....1..0....1..1....1..1....1..1....1..1....0..1....1..1 CROSSREFS Cf. A204084. Sequence in context: A203101 A060691 A075225 * A284494 A091541 A094354 Adjacent sequences: A204075 A204076 A204077 * A204079 A204080 A204081 KEYWORD nonn AUTHOR R. H. Hardin, Jan 10 2012 STATUS approved

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Last modified January 29 13:25 EST 2023. Contains 359923 sequences. (Running on oeis4.)