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A189855
Number of ways to place n nonattacking composite pieces rook + rider[2,4] on an n X n chessboard.
4
1, 2, 6, 24, 60, 208, 1184, 7840, 36036, 209664, 1395480, 10996728, 83573220, 723835856, 7132494776, 77976981216, 790552134804
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+2k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>2k for all i>=1, j>=1, k>=1, i+2k<=n, j+4k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved