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

1,4

Comments

Row 3 of A215788

Links

Table of n, a(n) for n=1..27.

Example

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

Crossrefs

Sequence in context: A364761 A009739 A062272 * A127137 A172239 A183758

Adjacent sequences: A215786 A215787 A215788 * A215790 A215791 A215792

Keyword

nonn

Author

R. H. Hardin Aug 23 2012

Status

approved