30以内（含30）的奇数有（ 1,3,5,7,9,11,13,15,17,19,21,23,25,27,29）,偶数有（2,4,6,8,10,12,14,16,18,20,22,24,26,28,30 ）,其中有因数5的数是（ 5,10,15,20,25,30）.
