A233611 Number of (n+2) X (1+2) 0..2 arrays with no increasing sequence of length 3 horizontally or diagonally downwards.

17064, 430608, 10864544, 274119232, 6916192896, 174499696896, 4402732038656, 111083570603008, 2802705126991872, 70713931738189824, 1784154920085856256, 45015298974634885120, 1135762998472268218368, 28655981812440693276672

Offset

1,1

Links

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

Formula

Empirical: a(n) = 26*a(n-1) - 16*a(n-2) - 88*a(n-3) + 48*a(n-4).

Empirical g.f.: 8*x*(2133 - 1632*x - 7280*x^2 + 4056*x^3) / ((1 - 2*x)*(1 - 24*x - 32*x^2 + 24*x^3)). - Colin Barker, Oct 11 2018

Example

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

Crossrefs

Column 1 of A233618.

Sequence in context: A252472 A233618 A233619 * A233610 A361349 A121669

Adjacent sequences: A233608 A233609 A233610 * A233612 A233613 A233614

Keyword

nonn

Author

R. H. Hardin, Dec 14 2013

Status

approved