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A189877
Number of ways to place n nonattacking composite pieces queen + rider[2,4] on an n X n chessboard.
2
1, 0, 0, 2, 0, 0, 0, 0, 0, 4, 56, 172, 680, 1348, 6576, 34568, 107624, 413760, 1697288, 8035558, 37441416, 192483420, 1115143224
OFFSET
1,4
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 AND |p(m+k)-p(m)|<>k for all i>=1, j>=1, m>=1, k>=1, i+2k<=n, j+4k<=n, m+k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved