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 A207142 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock having nonzero determinant and commuting with every horizontal or vertical neighbor. 1
 50, 30, 80, 62, 159, 122, 315, 242, 628, 482, 1254, 962, 2506, 1922, 5010, 3842, 10018, 7682, 20034, 15362, 40066, 30722, 80130, 61442, 160258, 122882, 320514, 245762, 641026, 491522, 1282050, 983042, 2564098, 1966082, 5128194, 3932162, 10256386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A207149. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) for n>8. Conjectures from Colin Barker, Jun 19 2018: (Start) G.f.: x*(50 - 20*x - 50*x^2 + 22*x^3 - 3*x^4 - x^5 - x^6 + x^7) / ((1 - x)*(1 - 2*x^2)). a(n) = 15 * 2^(n/2) + 2 for n>5 and even. a(n) = 313 * 2^((n-7)/2) + 2 for n>5 and odd. (End) EXAMPLE Some solutions for n=4: ..2..0....2..1....1..1....2..1....1..1....0..2....0..1....2..1....0..1....1..0 ..0..2....2..0....2..0....1..2....1..0....1..0....2..0....1..0....2..0....0..1 ..1..0....0..2....0..2....2..1....0..1....0..1....0..2....0..1....0..2....1..0 ..0..1....1..0....1..0....1..2....1..0....2..0....1..0....1..0....2..0....0..1 ..2..1....0..1....0..1....2..1....0..1....0..2....0..1....0..1....0..2....2..2 CROSSREFS Cf. A207149. Sequence in context: A033980 A342903 A207149 * A244277 A248688 A291495 Adjacent sequences: A207139 A207140 A207141 * A207143 A207144 A207145 KEYWORD nonn AUTHOR R. H. Hardin, Feb 15 2012 STATUS approved

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Last modified January 28 07:13 EST 2023. Contains 359850 sequences. (Running on oeis4.)