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A189568 Number of permutations p of 1,2,...,n satisfying |p(i+3)-p(i)|<>4 and |p(j+4)-p(j)|<>3 for all i=1..n-3, j=1..n-4. 3
1, 1, 2, 6, 24, 80, 326, 1566, 9544, 65036, 518498, 4750006, 48830634, 554929274, 6926227324, 93970452970, 1377573324202 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) is also the number of ways to place n nonattacking pieces rook + leaper[3,4] on an n X n chessboard.

LINKS

Table of n, a(n) for n=0..16.

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

FORMULA

Asymptotic: a(n)/n! ~ 1/e^4.

CROSSREFS

Cf. A137774, A189358, A189563, A189564, A189565, A189566, A189567.

Sequence in context: A275206 A095110 A189858 * A002742 A048120 A322198

Adjacent sequences:  A189565 A189566 A189567 * A189569 A189570 A189571

KEYWORD

nonn,more,hard

AUTHOR

Vaclav Kotesovec, Apr 23 2011

STATUS

approved

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Last modified May 15 22:06 EDT 2021. Contains 343933 sequences. (Running on oeis4.)