A248838 Number of length n arrays x(i), i=1..n with x(i) in 0..i and no value appearing more than 4 times.

2, 6, 24, 120, 718, 4994, 39556, 351320, 3456742, 37314126, 438366374, 5567209930, 75995663398, 1109556555434, 17252609166736, 284620418911180, 4965138989585412, 91317809653363376, 1765937111915469414

Offset: 1

Author

R. H. Hardin, Oct 15 2014

Keywords

• nonn

Comments

Column 4 of A248842

Examples

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

Links

• R. H. Hardin, Table of n, a(n) for n = 1..196