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A189838
Number of ways to place n nonattacking composite pieces rook + rider[2,2] on an n X n chessboard.
5
1, 2, 4, 16, 36, 128, 672, 4264, 25044, 173712, 1318904, 11069056, 96808692, 927478976, 9435033872, 103783608480, 1195155968388
OFFSET
1,2
COMMENTS
a(n) is also number of permutations p of 1,2,...,n satisfying |p(j+2k)-p(j)|<>2k for all j>=1, k>=1, j+2k<=n
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 29 2011
STATUS
approved