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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

Table of n, a(n) for n=1..18.

CROSSREFS

Cf. A062868, A196688.

Sequence in context: A219118 A005756 A206239 * A185457 A024250 A167140

Adjacent sequences:  A196684 A196685 A196686 * A196688 A196689 A196690

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 September 18 20:19 EDT 2020. Contains 337173 sequences. (Running on oeis4.)