1/2+(1/3+2/3)+(1/4+2/4+3/4)+...+(1/2002+2/2002+3/2002+...+2001/2002) =[1/2+)+(1/2002+2/2002+3/2002+...+2001/2002)]+...+[(1/1001+2/1001+...+1000/1001)+(1/1003+2/1003+...+1002/1003)]+(1/1002+2/1002+...+1001/1002) =1001+1001+...+1001+500.5 =1001×（2002/2-1)+500.5 =1001500.5