(1)若项数为偶数项2n则s偶-s奇=nds偶/s奇=An/An-1(n大于等于2)
(2)若项数为奇数项2n+1则s奇-s偶=An+1s奇=(n+1)An+1s偶=nAn+1s偶/s奇=n/n+1怎么推导出来的?
数列知识