A197469 Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,1,0,0,0 for x=0,1,2,3,4.

1, 2, 6, 12, 24, 50, 98, 194, 394, 786, 1562, 3138, 6282, 12530, 25082, 50210, 100330, 200658, 401498, 802818, 1605450, 3211442, 6422714, 12844514, 25690282, 51381138, 102759194, 205520322, 411044874, 822081650, 1644162938, 3288342434

Offset: 1

Author

R. H. Hardin, Oct 15 2011

Keywords

• nonn

Comments

Every 0 is next to 0 0's, every 1 is next to 1 1's, every 2 is next to 2 0's, every 3 is next to 3 0's, every 4 is next to 4 0's.

Column 2 of A197475.

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A197475.

Formula

Empirical: a(n) = a(n-1) +4*a(n-3) for n>6.

Empirical g.f.: x*(1 + x + 4*x^2 + 2*x^3 + 4*x^4 + 2*x^5) / ((1 - 2*x)*(1 + x + 2*x^2)). - Colin Barker, May 12 2018