A143892 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric under 90-degree rotation.

1, 2, 1, 5, 6, 29, 47, 300, 665, 5276, 15554, 160307, 632041, 8448701, 44021226

Offset

0,2

Links

Table of n, a(n) for n=0..14.

Example

Example: for n=3 the a(3)=5 solutions are
. . .   . . .   K . K   K . K   . K .
. . .   . K .   . . .   . K .   K . K
. . .   . . .   K . K   K . K   . K .

Crossrefs

Cf. A143870, A143875, A143881, A143886.

Cf. A143886, A143887, A143888, A143889, A143890, A143891, A143893.

Sequence in context: A125080 A349015 A217105 * A129321 A064642 A193630

Adjacent sequences: A143889 A143890 A143891 * A143893 A143894 A143895

Keyword

nonn,more,hard

Author

R. H. Hardin, Sep 04 2008

Status

approved