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A186464 Number of (n+1) X 2 0..2 arrays with every 2 X 2 subblock commuting with each of its horizontal and vertical 2 X 2 subblock neighbors. 2
81, 83, 277, 367, 966, 1321, 3078, 4553, 10028, 15650, 32786, 53166, 107524, 179614, 353932, 604474, 1168188, 2028530, 3863852, 6793514, 12800564, 22716978, 42458812, 75878698, 140963524, 253237282, 468324588, 844629530, 1556731220 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A186472.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) + a(n-2) - 4*a(n-3) + 4*a(n-4) - 2*a(n-5) for n>10.

Empirical g.f.: x*(81 - 79*x + 30*x^2 + 54*x^3 - 37*x^4 - 40*x^5 - 4*x^6 + 26*x^7 - 2*x^8 + x^9) / ((1 - x)*(1 - x - 2*x^2 + 2*x^3 - 2*x^4)). - Colin Barker, Feb 28 2018

EXAMPLE

Some solutions for 3 X 2:

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

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

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

CROSSREFS

Cf. A186472.

Sequence in context: A186472 A183984 A089784 * A345477 A295700 A286898

Adjacent sequences:  A186461 A186462 A186463 * A186465 A186466 A186467

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 22 2011

STATUS

approved

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Last modified June 22 04:06 EDT 2021. Contains 345367 sequences. (Running on oeis4.)