login
A189863
Number of ways to place n nonattacking composite pieces rook + rider[5,6] on an n X n chessboard.
0
1, 2, 6, 24, 120, 720, 4176, 26140, 185084, 1491098, 13285034, 132514356, 1321161252, 14181339764, 164574628260, 2057033314380
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+5k)-p(i)|<>6k AND |p(j+6k)-p(j)|<>5k for all i>=1, j>=1, k>=1, i+5k<=n, j+6k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved