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[0..1510] of extended;
    n,m,i,j,t:longint;

function pow(x,y:longint):extended;
  var i:longint;
  begin
    pow:=1;
    for i:=1 to y do 
      pow:=pow*x;
  end;

function C(n,m:longint):extended;
  var i:longint;
  begin
    C:=1;
    for i:=1 to m do
    begin
      C:=C*(i+m);
      C:=C/i;
    end;
  end;

begin
  f[1]:=1;
  for i:=2 to 1500 do
  begin
    j:=i-i and 1;
    f[i]:=f[i-1]+C(j,j shr 1)/pow(2,j);
  end;
  readln(t);
  for i:=1 to t do
  begin
    readln(n);
    writeln('Case ',i,': ',f[n]:0:6);
  end;
end.