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a(n) = floor(n!/2^n).
3

%I #12 Aug 21 2021 13:34:43

%S 0,0,0,1,3,11,39,157,708,3543,19490,116943,760134,5320940,39907054,

%T 319256437,2713679718,24423117468,232019615953,2320196159531,

%U 24362059675078,267982656425859,3081800548897382,36981606586768593

%N a(n) = floor(n!/2^n).

%H Harry J. Smith, <a href="/A066979/b066979.txt">Table of n, a(n) for n = 1..150</a>

%t Table[Floor[n!/2^n],{n,30}] (* _Harvey P. Dale_, Aug 21 2021 *)

%o (PARI) { for (n=1, 150, write("b066979.txt", n, " ", floor(n!/2^n)) ) } \\ _Harry J. Smith_, Apr 14 2010

%K nonn

%O 1,5

%A _Benoit Cloitre_, Jan 26 2002