1/(2*4)+1/(4*6)+1/(6*8)+......+1/(2006*2008)=1/2(1/2-1/4+1/4-1/6+1/6-1/8+.....+1/2006-1/2008)=1/2(1/2-1/2008)=1/2*1003/2008=1004/4016
