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A189852
Number of ways to place n nonattacking composite pieces rook + rider[1,5] on an n X n chessboard.
4
1, 2, 6, 24, 120, 336, 1474, 8340, 57756, 475658, 2812910, 20852460, 181255892, 1817101242, 20435345782, 197871434994
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>k for all i>=1, j>=1, k>=1, i+k<=n, j+5k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved