A248837 Number of length n arrays x(i), i=1..n with x(i) in 0..i and no value appearing more than 3 times.

2, 6, 24, 118, 686, 4598, 34872, 295044, 2753958, 28103804, 311216626, 3716341042, 47597786154, 650812077852, 9461423560788, 145724617925326, 2370293673319292, 40600119927220706, 730458115445479734, 13772063820971722638

Offset: 1

Author

R. H. Hardin, Oct 15 2014

Keywords

• nonn

Comments

Column 3 of A248842.

Essentially the same as A135106. - Georg Fischer, Oct 23 2018

Examples

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

Links

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