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A189861
Number of ways to place n nonattacking composite pieces rook + rider[4,5] on an n X n chessboard.
1
1, 2, 6, 24, 120, 552, 2826, 17080, 117816, 943250, 7369128, 63533572, 603300392, 6280101222, 71927971040, 836503868762
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(i+4k)-p(i)|<>5k AND |p(j+5k)-p(j)|<>4k for all i>=1, j>=1, k>=1, i+4k<=n, j+5k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved