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A189282 Number of permutations p of 1,2,...,n satisfying p(i+3)-p(i)<>3 for all 1<=i<=n-3. 5
1, 1, 2, 6, 22, 98, 534, 3414, 25498, 217338, 2080990, 22076030, 256888218, 3252308706, 44497313158, 654139144158, 10281397705242, 172033123244330, 3052895403376110, 57266799403366334, 1132124282036449570, 23524895818926592242 (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[3,3] on an n X n chessboard.

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..30 (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 + 5/n + 6/n^2)/e.

CROSSREFS

Cf. A000255, A189281, A117574.

Sequence in context: A054096 A006183 A189844 * A318974 A012269 A012272

Adjacent sequences:  A189279 A189280 A189281 * A189283 A189284 A189285

KEYWORD

nonn,hard

AUTHOR

Vaclav Kotesovec, Apr 19 2011

EXTENSIONS

Terms a(29)-a(30) from Vaclav Kotesovec, Apr 20 2012

STATUS

approved

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Last modified June 15 11:44 EDT 2021. Contains 345048 sequences. (Running on oeis4.)