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A196687 n!*A062868(n). 2
1, 4, 24, 336, 5520, 203040, 7025760, 510370560, 30163311360, 3577017024000, 319851801561600, 55850407258060800, 7021439018770176000, 1692163531361176473600, 284409062346887622144000, 90395009213694143422464000, 19571060809440210728706048000, 7929132907666579072319471616000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Let p = (p1..pn) and q = (q1..qn) be two random permutations of (1..n); call the pair (p,q) balanced if the number of i with pi > qi is the same as the number of i with pi < qi. Then a(n) is the number of balanced pairs.
LINKS
CROSSREFS
Sequence in context: A005756 A206239 A361054 * A185457 A024250 A167140
KEYWORD
nonn
AUTHOR
Jan Lakota, Oct 04 2011
EXTENSIONS
a(1)-a(6) computed by Jan Lakota; extended by N. J. A. Sloane, Oct 04 2011
STATUS
approved

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Last modified May 23 18:59 EDT 2024. Contains 372765 sequences. (Running on oeis4.)