A236271 Number of (n+1) X (1+1) 0..2 arrays with the upper median unequal to the lower median in every 2 X 2 subblock.

42, 208, 1048, 5328, 27168, 138720, 708640, 3620768, 18501536, 94542752, 483118496, 2468772768, 12615641504, 64467060640, 329432556960, 1683430581152, 8602485031328, 43959490084768, 224637040795040, 1147915959163808

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 5*a(n-1) + 4*a(n-2) - 16*a(n-3) - 8*a(n-4).

Empirical g.f.: 2*x*(21 - x - 80*x^2 - 36*x^3) / ((1 - 2*x)*(1 - 3*x - 10*x^2 - 4*x^3)). - Colin Barker, Oct 21 2018

Example

Some solutions for n=5:
..1..0....1..0....2..1....1..0....0..1....0..2....1..2....1..2....2..1....0..2
..0..1....2..0....0..2....2..0....0..2....2..1....0..2....0..2....1..2....1..2
..0..2....1..2....2..0....2..0....2..1....1..2....0..2....1..2....0..0....2..1
..0..2....2..0....1..0....0..2....0..0....0..2....2..0....1..2....2..2....2..1
..1..0....1..2....1..0....0..2....2..2....2..0....1..0....0..0....0..1....0..0
..2..0....0..0....1..0....2..0....1..0....1..2....1..0....1..2....2..0....2..1

Crossrefs

Column 1 of A236278.

Sequence in context: A299056 A299817 A236278 * A008446 A255424 A122232

Adjacent sequences: A236268 A236269 A236270 * A236272 A236273 A236274

Keyword

nonn

Author

R. H. Hardin, Jan 21 2014

Status

approved