1/2*4+1/6*8+······+1/2006*2008+1/4*6+1/8*10+······+1/2004*2006=1/2*4+1/4*6+1/6*8+18*10+······+1/2004*2006+1/2006*2008=1/2*(1/2-1/4)+1/2*(1/4-1/6)+1/2*(1/6-1/8)+1/2*(1/8-1/10)+.+1/2*(...