编写程序, 输入n,求表 式1+(1+2)+(1+2+3)+(1+2+3+4)++(1+2+3+.+n)的値。
n = int(input()) s = sum((i+1)*(n-i) for i in range(n)) print(s)
n=int(input()) s=0 for i in range(1,n+1): s+=sum(range(1,i+1)) print(s)