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%I #6 Dec 22 2020 03:12:27
%S 1,12,316,4961,88482,1456780,24970807,430069638,7646066285,
%T 139512608803,2630205520242,51191324887317,1030225266241718,
%U 21431850533761458,460916811387051427,10243049068068285706,235127217600172319772,5571780677576178939683
%N Number of permutations of [n] having exactly four (possibly overlapping) doubledescents.
%H Alois P. Heinz, <a href="/A279293/b279293.txt">Table of n, a(n) for n = 6..461</a>
%F 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
%Y Column k=4 of A162975.
%K nonn
%O 6,2
%A _Alois P. Heinz_, Dec 09 2016
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