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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
Christoph Koutschan, Table of n, a(n) for n = 0..48 (terms 0..30 from Vaclav Kotesovec, terms 31..36 from Manuel Kauers and Christoph Koutschan, terms 37..48 from George Spahn and Doron Zeilberger)
Vaclav Kotesovec, Non-attacking chess pieces, 6ed, 2013, p. 644.
FORMULA
Asymptotics: a(n)/n! ~ (1 + 5/n + 6/n^2)/e.
CROSSREFS
Sequence in context: A054096 A006183 A189844 * A318974 A012269 A012272
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 19 2011
STATUS
approved

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Last modified December 1 20:47 EST 2023. Contains 367502 sequences. (Running on oeis4.)