题解 | #牛牛学数列4#
牛牛学数列4
https://www.nowcoder.com/practice/586b114f52034688879342ba45779081
def a(n): # 通项公式
if n == 1:
return 1
return n + a(n-1)
def s(n): # 前n项和
if n == 1:
return 1
return a(n) + s(n-1)
n = int(input())
print(s(n))
#题解#