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A186474 Number of (n+1) X 2 0..3 arrays with every 2 X 2 subblock commuting with each of its horizontal and vertical 2 X 2 subblock neighbors. 2
256, 205, 1098, 1251, 4895, 5955, 20079, 27101, 84228, 123227, 354915, 553287, 1501107, 2465976, 6374253, 10928793, 27157017, 48218637, 116026140, 211997451, 496891083, 929460999, 2132220387, 4065922560, 9164874045, 17754363633 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A186482.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + 2*a(n-2) - 6*a(n-3) + 6*a(n-4) - 3*a(n-5) for n>12.

Empirical g.f.: x*(256 - 307*x + 176*x^2 + 181*x^3 - 109*x^4 - 211*x^5 - 88*x^6 + 191*x^7 - 19*x^8 - 2*x^9 + 2*x^10 + 2*x^11) / ((1 - x)*(1 - x - 3*x^2 + 3*x^3 - 3*x^4)). - Colin Barker, Feb 28 2018

EXAMPLE

Some solutions for 3 X 2:

..0..0....2..2....3..3....3..3....2..0....2..2....2..3....0..2....2..0....0..0

..3..0....0..0....1..0....3..3....0..2....1..0....3..0....3..0....0..2....1..0

..0..3....0..0....0..1....3..3....1..2....0..1....0..3....0..3....0..0....1..1

CROSSREFS

Cf. A186482.

Sequence in context: A103949 A057066 A186482 * A093861 A248776 A223600

Adjacent sequences:  A186471 A186472 A186473 * A186475 A186476 A186477

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 22 2011

STATUS

approved

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Last modified April 20 09:21 EDT 2021. Contains 343125 sequences. (Running on oeis4.)