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A189283 Number of permutations p of 1,2,...,n satisfying p(i+4)-p(i)<>4 for all 1<=i<=n-4. 4
1, 1, 2, 6, 24, 114, 628, 4062, 30360, 255186, 2414292, 25350954, 292378968, 3673917102, 49928069188, 729534877758, 11403682481112, 189862332575658, 3354017704180052, 62654508729565554, 1233924707891272728, 25550498290562247438 (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[4,4] on an n X n chessboard.

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..27 (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 + 7/n + 12/n^2)/e.

CROSSREFS

Cf. A000255, A189281, A189282, A189255.

Sequence in context: A171448 A068199 A189846 * A177522 A216717 A174072

Adjacent sequences:  A189280 A189281 A189282 * A189284 A189285 A189286

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 June 20 12:04 EDT 2021. Contains 345164 sequences. (Running on oeis4.)