login
A189860
Number of ways to place n nonattacking composite pieces rook + rider[3,6] on an n X n chessboard.
2
1, 2, 6, 24, 120, 720, 3312, 18688, 127104, 990208, 8878016, 89267712, 789509184, 7803741824, 85447337472, 1008717911040
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>3k for all i>=1, j>=1, k>=1, i+3k<=n, j+6k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved