1+3+5+7+``````+（2n-1）+（2n+1）+（2n+3）和103+105+107+······+2003+

1+3+5+7+``````+（2n-1）+（2n+1）+（2n+3）=（1+2n+3）（n+2)/2
=（n+2)^2
103+105+107+······+2003+2005
=(103+2005)*((2005-103)/2+1)