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%I #9 Apr 04 2019 09:54:30
%S 1,1,1,2,3,4,8,10,20,26,51,64,128,163,326,416,834,1067,2148,2755,5559,
%T 7147,14449,18613,37696,48638,98650,127463,258857,334864,680822,
%U 881657,1794294,2325750,4737361
%N a(n) = floor(n^(n/2)/n!!).
%C This sequence is a second approximation of a double factorial analog to Stirling's approximation to factorial. Note that a(n) is exact for n = 1, 2, 4.
%F a(n) = floor(n^(n/2)/n!!). a(n) = floor(sqrt(A000312(n))/A006882(n)).
%e a(10) = floor((10^5)/3840) = floor(26.0416667) = 26.
%e a(11) = floor((11^5.5)/10395) = floor(51.3848715) = 51.
%p A114854 := proc(n)
%p n^(n/2)/doublefactorial(n) ;
%p floor(%) ;
%p end proc:
%p seq(A114854(n),n=1..35) ; # _R. J. Mathar_, Jun 23 2014
%t Table[Floor[n^(n/2)/n!!],{n,40}] (* _Harvey P. Dale_, Apr 04 2019 *)
%Y Cf. A000312, A006882, A055775.
%K easy,nonn
%O 1,4
%A _Jonathan Vos Post_, Feb 20 2006
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