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 A117574 Total number of permutations p of [n] such that |p(i+3) - p(i)| is not equal to 3 for 1 <= i <= n-3. 9
 1, 2, 6, 20, 80, 384, 2240, 15424, 123456, 1110928, 11287232, 127016304, 1565107248, 20935873872, 301974271248, 4669727780624, 77046043259824, 1350585114106416, 25062108668100208, 490725684463001488, 10109820295907492304 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is also number of ways to place n nonattacking pieces rook + leaper[3,3] on an n X n chessboard. REFERENCES Roberto Tauraso, The Dinner Table Problem: The Rectangular Case, INTEGERS, vol. 6 (2006), paper A11. LINKS Vaclav Kotesovec, Table of n, a(n) for n = 1..30 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 Formula given in Tauraso reference. Asymptotic (R. Tauraso 2006, quadratic term V. Kotesovec 2011): a(n)/n! ~ (1 + 8/n + 30/n^2)/e^2. CROSSREFS Cf. A002464, A110128. Sequence in context: A245373 A204440 A189839 * A177481 A177475 A118476 Adjacent sequences:  A117571 A117572 A117573 * A117575 A117576 A117577 KEYWORD nonn,hard AUTHOR James A. Sellers, Apr 27 2006 EXTENSIONS Terms a(17)-a(28) from Vaclav Kotesovec, Apr 19 2011 Terms a(29)-a(30) from Vaclav Kotesovec, Apr 20 2012 STATUS approved

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Last modified July 25 23:39 EDT 2021. Contains 346294 sequences. (Running on oeis4.)