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A189564
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Number of permutations p of 1,2,...,n satisfying |p(i+1)-p(i)|<>5 and |p(j+5)-p(j)|<>1 for all i=1..n-1, j=1..n-5.
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7
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1, 2, 6, 24, 120, 336, 1474, 8340, 57756, 475658, 4171070, 41950294, 472535256, 5882635676, 79963449714, 1173614446044
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OFFSET
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1,2
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COMMENTS
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a(n) is also the number of ways to place n nonattacking pieces rook + leaper[1,5] on an n X n chessboard.
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LINKS
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Table of n, a(n) for n=1..16.
V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)
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FORMULA
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Asymptotic: a(n)/n! ~ 1/e^4.
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CROSSREFS
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Cf. A137774, A189358, A189563.
Sequence in context: A000804 A048631 A189852 * A178010 A062348 A189856
Adjacent sequences: A189561 A189562 A189563 * A189565 A189566 A189567
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KEYWORD
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nonn,hard
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AUTHOR
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Vaclav Kotesovec, Apr 23 2011
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STATUS
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approved
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