A209497 Number of n X 2 0..4 arrays with every 2 X 2 subblock containing exactly one value repeat, and new values 0..4 introduced in row major order.

2, 6, 57, 690, 9393, 133380, 1920126, 27760512, 401882796, 5820335088, 84304518360, 1221153876288, 17688664980912, 256224877720896, 3711487617186912, 53761934301895680, 778756709322725568

Offset: 1

Author

R. H. Hardin, Mar 09 2012

Keywords

• nonn

Comments

Column 2 of A209503.

Examples

			Some solutions for n=4.
..0..0....0..0....0..1....0..0....0..0....0..0....0..0....0..0....0..1....0..0
..1..2....1..2....0..2....1..2....1..2....1..2....1..2....1..2....1..2....1..2
..3..1....2..0....1..0....0..1....2..3....0..2....1..0....0..1....0..2....2..3
..2..1....0..3....2..0....0..2....2..1....3..2....2..0....2..1....1..0....4..2
		

Links

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

Crossrefs

Cf. A209503.

Formula

Empirical: a(n) = 16*a(n-1) - 10*a(n-2) - 168*a(n-3) - 72*a(n-4) for n>5.

Empirical g.f.: x*(2 - 26*x - 19*x^2 + 174*x^3 + 75*x^4) / ((1 - 4*x - 2*x^2)*(1 - 12*x - 36*x^2)). - Colin Barker, Jul 10 2018