1/（1X3）+1/(3X5)+1/(5X7)+........+1/(4025X4027)=1/2X(1-1/3+1/3-1/5+1/5-1/7+.....+1/4025-1/4027)=1/2X(1-1/4027)=1/2X4026/4027=2013/4027
