A143890 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric about both diagonal and antidiagonal.

1, 2, 3, 9, 16, 61, 143, 802, 2265, 17236, 59156, 631443, 2686969, 39237301, 210001256

Offset

0,2

Links

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

Crossrefs

Sequence in context: A289452 A086771 A156066 * A270339 A272057 A056658

Adjacent sequences: A143887 A143888 A143889 * A143891 A143892 A143893

Keyword

nonn,more,hard

Author

R. H. Hardin, Sep 04 2008

Status

approved