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A207144 Number of (n+1) X 4 0..2 arrays with every 2 X 2 subblock having nonzero determinant and commuting with every horizontal or vertical neighbor. 1
80, 56, 157, 110, 311, 218, 619, 434, 1235, 866, 2468, 1730, 4934, 3458, 9866, 6914, 19730, 13826, 39458, 27650, 78914, 55298, 157826, 110594, 315650, 221186, 631298, 442370, 1262594, 884738, 2525186, 1769474, 5050370, 3538946, 10100738, 7077890 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 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>10.

Empirical g.f.: x*(80 - 24*x - 59*x^2 + x^3 - x^4 + x^5 - x^6 + x^7 - x^8 + x^9) / ((1 - x)*(1 - 2*x^2)). - Colin Barker, Jun 19 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

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

CROSSREFS

Cf. A207149.

Sequence in context: A239131 A033400 A306414 * A200720 A220088 A126783

Adjacent sequences:  A207141 A207142 A207143 * A207145 A207146 A207147

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 15 2012

STATUS

approved

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Last modified January 28 05:27 EST 2022. Contains 350654 sequences. (Running on oeis4.)