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A183330 Number of n X 2 binary arrays with each 1 adjacent to exactly two 0's. 2
1, 7, 10, 23, 49, 98, 209, 431, 898, 1871, 3889, 8098, 16849, 35063, 72970, 151847, 316001, 657602, 1368481, 2847839, 5926402, 12332959, 25665121, 53409602, 111146401, 231297767, 481335050, 1001667383, 2084488849, 4337860898 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A183335.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = a(n-1) + 2*a(n-2) + a(n-3) - a(n-4).

Empirical g.f.: x*(1 + 6*x + x^2 - 2*x^3) / (1 - x - 2*x^2 - x^3 + x^4). - Colin Barker, Feb 27 2018

EXAMPLE

Some solutions for 7 X 2:

..0..0....0..0....0..1....1..0....1..0....0..0....1..0....0..0....1..0....0..0

..1..1....0..0....0..0....0..0....0..1....1..0....0..0....1..1....0..0....1..1

..0..0....1..1....1..1....1..1....0..1....1..0....0..0....0..0....1..1....0..0

..1..1....0..0....0..0....0..0....0..0....0..0....1..0....0..0....0..0....0..0

..0..0....1..1....1..1....0..0....1..0....0..0....1..0....0..0....1..1....1..0

..0..0....0..0....0..0....0..0....1..0....0..0....0..0....0..0....0..0....1..0

..1..0....0..0....1..0....0..1....0..0....0..0....0..1....1..0....0..1....0..0

CROSSREFS

Cf. A183335.

Sequence in context: A074377 A103119 A054224 * A196316 A134329 A175492

Adjacent sequences:  A183327 A183328 A183329 * A183331 A183332 A183333

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 03 2011

STATUS

approved

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Last modified May 18 21:28 EDT 2022. Contains 353825 sequences. (Running on oeis4.)