A185560 1/4 the number of n X n 0..3 arrays with no element equal both to the element above and to the element to its left.

1, 60, 50580, 598507920, 99407416968000, 231753101877188629380, 7583858300260627032845531520, 3483475434832751291309593655505225600, 22459143127863154464679826472043109609252549520

Offset: 1

Author

R. H. Hardin Jan 31 2011

Keywords

• nonn

Comments

Diagonal of A185567

Examples

			Some solutions for 3X3 with a(1,1)=0
..0..1..2....0..3..2....0..0..0....0..3..2....0..2..1....0..0..0....0..0..3
..3..1..1....1..2..0....1..2..2....0..0..0....1..3..0....0..2..0....3..3..0
..3..3..1....1..2..0....3..3..3....1..1..3....0..1..3....0..0..2....0..0..1
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..10