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A189851
Number of ways to place n nonattacking composite pieces rook + rider[1,4] on an n X n chessboard.
5
1, 2, 6, 24, 48, 182, 868, 5752, 22952, 131766, 912964, 7556978, 52602390, 432795244, 4121203656, 44335718598, 416447624724
OFFSET
1,2
COMMENTS
In fairy chess, the rider [1,4] is called a Girafferider.
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=n, j+4k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved