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A274997
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Number of permutations of [n] having exactly one doubledescent.
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2
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0, 0, 0, 1, 6, 41, 274, 2040, 16346, 143571, 1365354, 14056287, 155638724, 1847352720, 23400880036, 315270938501, 4502081195166, 67941159822229, 1080528172834710, 18065046986905320, 316769071197428286, 5813469963339136855, 111449225620923739458
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OFFSET
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0,5
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LINKS
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FORMULA
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a(n) ~ c * 3^(3*n/2) * n^(n+3/2) / (exp(n) * 2^n * Pi^n), where c = 0.827206526063705458546024... . - Vaclav Kotesovec, Dec 11 2016
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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