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A189271
Number of permutations p of 1,2,...,n satisfying |p(i+6)-p(i)|<>6 for all 1<=i<=n-6.
4
1, 2, 6, 24, 120, 720, 4800, 34752, 280512, 2528256, 25282560, 278323200, 3289036800, 42336448512, 589351062528, 8820501301248, 141215147788800, 2407845089203200, 43543159894318080, 832618225074748416, 16782891792284791296
OFFSET
1,2
COMMENTS
a(n) is also number of ways to place n nonattacking pieces rook + leaper[6,6] on an n X n chessboard.
LINKS
Vaclav Kotesovec, Non-attacking chess pieces, Sixth edition, p. 633, Feb 02 2013.
Roberto Tauraso, The Dinner Table Problem: The Rectangular Case, INTEGERS: Electronic Journal of Combinatorial Number Theory, Vol. 6 (2006), #A11.
FORMULA
Asymptotic (R. Tauraso 2006, quadratic term V. Kotesovec 2011): a(n)/n! ~ (1 + 20/n + 168/n^2)/e^2.
Generally (for this sequence is d=6): 1/e^2*(1+4(d-1)/n+2d*(3d-4)/n^2+...).
CROSSREFS
Column k=6 of A333706.
Sequence in context: A152362 A177543 A189842 * A152366 A147740 A147739
KEYWORD
nonn,hard
AUTHOR
Vaclav Kotesovec, Apr 19 2011
EXTENSIONS
Terms a(23)-a(24) from Vaclav Kotesovec, Apr 21 2012
STATUS
approved