A242543 Number of length n+3 0..2 arrays with no four elements in a row with pattern aabb (possibly a=b) and new values 0..2 introduced in 0..2 order.

12, 32, 88, 242, 660, 1800, 4920, 13448, 36736, 100352, 274176, 749088, 2046528, 5591168, 15275392, 41733248, 114017280, 311500800, 851036160, 2325074432, 6352221184, 17354590208, 47413622784, 129536428032, 353900101632

Offset: 1

Author

R. H. Hardin, May 17 2014

Keywords

• nonn

Comments

Column 2 of A242549

Examples

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

Links

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

Formula

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

Empirical: G.f.: -2*x*(6+4*x+12*x^2+9*x^3) / ( (2*x^2+2*x-1)*(2*x^2+1) ). - R. J. Mathar, May 18 2014