A143888 Number of ways of placing kings with no more than 4 mutual attacks on an n X n chessboard symmetric under horizontal and vertical reflection.

1, 2, 1, 11, 4, 101, 29, 1592, 263, 43578, 4424, 1972239, 117557, 159790891, 5394252, 22035879309, 430235439

Offset

0,2

Links

Table of n, a(n) for n=0..16.

Crossrefs

Sequence in context: A285996 A191618 A306547 * A016546 A303611 A356446

Adjacent sequences: A143885 A143886 A143887 * A143889 A143890 A143891

Keyword

nonn,more,hard

Author

R. H. Hardin, Sep 04 2008

Status

approved