A268450 Number of length-n 0..n arrays with no adjacent pair x,x+1 followed at any distance by x+1,x.

2, 9, 61, 581, 7160, 108032, 1926444, 39616567, 922677334, 24000231919, 689530024294, 21683683196634, 740776505063512, 27318331535557441, 1081605306266896792, 45759587251345781091, 2060162120919764963754

Offset: 1

Author

R. H. Hardin, Feb 04 2016

Keywords

• nonn

Comments

Diagonal of A268457.

Examples

			Some solutions for n=6
..0....3....1....3....5....3....6....1....6....3....1....2....2....5....1....3
..1....0....1....5....3....1....6....4....3....6....2....2....3....0....1....5
..3....6....2....1....5....5....4....2....3....6....2....1....1....1....2....5
..6....1....6....1....5....4....3....5....0....2....0....5....6....4....4....1
..1....2....4....2....3....1....1....5....2....0....1....5....3....2....0....0
..3....6....4....2....3....6....2....1....0....0....1....1....4....1....4....1
		

Crossrefs

Cf. A268457.