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A189858
Number of ways to place n nonattacking composite pieces rook + rider[3,4] on an n X n chessboard.
1
1, 2, 6, 24, 80, 326, 1566, 9544, 53696, 347382, 2566892, 21907934, 184868860, 1704360992, 17294597926, 192725663600, 2139133978996
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+3k)-p(i)|<>4k AND |p(j+4k)-p(j)|<>3k for all i>=1, j>=1, k>=1, i+3k<=n, j+4k<=n.
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved