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.

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

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