[(2n+1)+1]/2=(2n+2)/2=n+1
1+3+5+.+(2n-1)+(2n+1)
=[(2n+1)+1]*(n+1)/2
=（2n+2)/2*(n+1)
=（n+1)*(n+1)
1+3+5+.+99=2500=50*50