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A189255 Number of permutations p of 1,2,...,n satisfying |p(i+4)-p(i)|<>4 for all 1<=i<=n-4. 5
1, 2, 6, 24, 108, 544, 3264, 23040, 176832, 1563392, 15536160, 171172224, 2066033472, 27146652480, 385447394880, 5878028516736, 95776238793504, 1660164417866304, 30496085473606944, 591661117634375040, 12087628978334638752 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) is also number of ways to place n nonattacking pieces rook + leaper[4,4] on an n X n chessboard.

REFERENCES

Roberto Tauraso, The Dinner Table Problem: The Rectangular Case, INTEGERS, vol. 6 (2006), paper A11.

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..27

V. Kotesovec, Number of ways of placing non-attacking queens, kings, bishops and knights (in English and Czech)

Vaclav Kotesovec, Mathematica program for this sequence

FORMULA

Asymptotic (R. Tauraso 2006, quadratic term V. Kotesovec 2011): a(n)/n! ~ (1 + 12/n + 64/n^2)/e^2.

CROSSREFS

Cf. A002464, A110128, A117574.

Sequence in context: A178594 A277248 A189840 * A230695 A177519 A214762

Adjacent sequences:  A189252 A189253 A189254 * A189256 A189257 A189258

KEYWORD

nonn,hard

AUTHOR

Vaclav Kotesovec, Apr 19 2011

EXTENSIONS

Terms a(26)-a(27) from Vaclav Kotesovec, Apr 20 2012

STATUS

approved

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Last modified February 20 15:01 EST 2018. Contains 299380 sequences. (Running on oeis4.)