A215789 Number of permutations of 0..floor((3*n-1)/2) on even squares of an 3*n array such that each row, column, diagonal and (downwards) antidiagonal of even squares is increasing.

1, 1, 1, 2, 5, 12, 42, 110, 462, 1274, 6006, 17136, 87516, 255816, 1385670, 4124406, 23371634, 70549050, 414315330, 1264752060, 7646001090, 23555382240, 145862174640, 452806924752, 2861142656400, 8939481277552, 57468093927120

Offset: 1

Author

R. H. Hardin Aug 23 2012

Keywords

• nonn

Comments

Row 3 of A215788

Examples

			Some solutions for n=5
..0..x..1..x..2....0..x..1..x..3....0..x..1..x..3....0..x..1..x..2
..x..3..x..5..x....x..2..x..5..x....x..2..x..4..x....x..3..x..4..x
..4..x..6..x..7....4..x..6..x..7....5..x..6..x..7....5..x..6..x..7