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A189285 Number of permutations p of 1,2,...,n satisfying p(i+6)-p(i)<>6 for all 1<=i<=n-6. 2
1, 1, 2, 6, 24, 120, 720, 4920, 37488, 319644, 3033264, 31784280, 364902480, 4538652840, 61102571376, 885045657564, 13722397569072, 226742901078120, 3977354871110160, 73816786920489720, 1444940702597713008, 29750236302549282948 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) is also number of ways to place n nonattacking pieces rook + semi-leaper[6,6] on an n X n chessboard.

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..24 (Updated Jan 19 2019)

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 (V. Kotesovec, Mar 2011): a(n)/n! ~ (1 + 11/n + 30/n^2)/e.

Generally (for this sequence is d=6): 1/e*(1+(2d-1)/n+d*(d-1)/n^2).

CROSSREFS

Cf. A000255, A189281, A189282, A189283, A189284, A189271.

Sequence in context: A177540 A068201 A189848 * A177545 A177538 A177550

Adjacent sequences:  A189282 A189283 A189284 * A189286 A189287 A189288

KEYWORD

nonn,hard

AUTHOR

Vaclav Kotesovec, Apr 19 2011

EXTENSIONS

Terms a(23)-a(24) from Vaclav Kotesovec, Apr 21 2012

STATUS

approved

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Last modified August 1 02:49 EDT 2021. Contains 346379 sequences. (Running on oeis4.)