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A279293
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Number of permutations of [n] having exactly four (possibly overlapping) doubledescents.
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2
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1, 12, 316, 4961, 88482, 1456780, 24970807, 430069638, 7646066285, 139512608803, 2630205520242, 51191324887317, 1030225266241718, 21431850533761458, 460916811387051427, 10243049068068285706, 235127217600172319772, 5571780677576178939683
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OFFSET
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6,2
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LINKS
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FORMULA
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a(n) ~ c * 3^(3*n/2) * n^(n + 9/2) / (exp(n) * 2^n * Pi^n), where c = 0.000357063672536829943422824320618... . - Vaclav Kotesovec, Dec 22 2020
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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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