1+3+7+9+…+(2n-1)+(2n+1)+(2n+3)等于几

问题描述:

1+3+7+9+…+(2n-1)+(2n+1)+(2n+3)等于几

=(1+2n+3)+(3+2n+1)+(7+2n-1)+.
=(2n+4)*(n+2)
=2(n+2)的平方