bzoj2489

这种题完全可以暴力找规律，暴力打表各种搞法

这里有一篇比较全面的题解：http://acm.uestc.edu.cn/bbs/read.php?tid=3698&page=1&toread=1#tpc

 var f:array[..] of extended;
     n,m,i,j,t:longint;

 function pow(x,y:longint):extended;
   var i:longint;
   begin
     pow:=;
     for i:= to y do
       pow:=pow*x;
   end;

 function C(n,m:longint):extended;
   var i:longint;
   begin
     C:=;
     for i:= to m do
     begin
       C:=C*(i+m);
       C:=C/i;
     end;
   end;

 begin
   f[]:=;
   for i:= to  do
   begin
     j:=i-i and ;
     f[i]:=f[i-]+C(j,j shr )/pow(,j);
   end;
   readln(t);
   for i:= to t do
   begin
     readln(n);
     writeln('Case ',i,': ',f[n]::);
   end;
 end.