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A279292
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Number of permutations of [n] having exactly three (possibly overlapping) doubledescents.
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2
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1, 10, 167, 2064, 28143, 374166, 5227491, 75105984, 1127851278, 17625022976, 287569327286, 4891520843344, 86749331150517, 1602239541108282, 30795187124606301, 615261376037422992, 12764913390565572333, 274721686459213597782, 6126847681304067647287
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OFFSET
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5,2
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LINKS
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FORMULA
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a(n) ~ c * 3^(3*n/2) * n^(n+7/2) / (exp(n) * 2^n * Pi^n), where c = 0.0065517603957816327489026... . - 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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