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 A204609 Number of (n+1) X 2 0..1 arrays with the determinants of 2 X 2 subblocks nondecreasing rightwards and downwards. 4
 16, 47, 125, 335, 907, 2470, 6740, 18406, 50278, 137354, 375250, 1025194, 2800874, 7652122, 20905978, 57116186, 156044314, 426320986, 1164730586, 3182103130, 8693667418, 23751541082, 64890416986, 177283916122, 484348666202 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Column 1 of A204616. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 FORMULA Empirical: a(n) = 3*a(n-1) - 2*a(n-3) for n>6. Conjectures from Colin Barker, Feb 20 2018: (Start) G.f.: (16 - x - 16*x^2 - 8*x^3 - 4*x^4 - x^5) / ((1 - x)*(1 - 2*x - 2*x^2)). a(n) = (112 + (193-113*sqrt(3))*(1-sqrt(3))^n + (1+sqrt(3))^n*(193+113*sqrt(3))) / 24 for n>2. (End) EXAMPLE Some solutions for n=4: ..1..1....1..0....0..0....0..0....1..1....1..1....1..0....1..0....0..0....1..1 ..1..1....0..0....1..0....0..1....0..0....0..0....0..0....0..0....0..1....1..1 ..1..1....0..1....0..0....0..0....0..0....0..0....1..0....0..1....0..1....1..1 ..0..0....0..1....0..1....1..0....0..1....1..1....1..1....0..1....0..1....1..1 ..1..1....0..0....0..1....1..0....0..1....1..1....0..1....0..1....0..1....1..1 CROSSREFS Cf. A204616. Sequence in context: A204800 A194268 A292171 * A233063 A208634 A333602 Adjacent sequences: A204606 A204607 A204608 * A204610 A204611 A204612 KEYWORD nonn AUTHOR R. H. Hardin, Jan 17 2012 STATUS approved

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Last modified September 25 15:05 EDT 2023. Contains 365648 sequences. (Running on oeis4.)