等差数列2,5,7,9.(3N-1)的积

问题描述:

等差数列2,5,7,9.(3N-1)的积

老兄,2,5,7,9不是等差数列,你打错了,题目应该是2,5,8,11……(3N-1)吧
而且等差数列一般是求和的,这个数列的和S=(2+3N-1)x N/2=1.5N²+0.5N