



0, 0, 6, 120, 4440, 157680, 9187920, 557665920, 50759291520, 4795586208000, 636749560339200, 86796062772249600, 15877174512431232000, 2953945462595410483200, 712801595188655900928000, 173684063741850454560768000, 53471242848053479728254976000, 16530628080065352033845256192000
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OFFSET

1,3


COMMENTS

Let p = (p1..pn) and q = (q1..qn) be two random permutations of (1..n); call the pair (p,q) positive if the number of i with pi > qi is greater than the number of i with pi < qi. Then a(n) is the number of positive pairs.


LINKS



CROSSREFS



KEYWORD

nonn


AUTHOR

Jan Lakota, Oct 04 2011


EXTENSIONS



STATUS

approved



