In a land far, far away all the lily pads grow in a straight line across the rivers and are always the same distance apart. Frogs when they jump from lily pad to lily pad can either go to the adjacent lily pad of jump over the adjacent lily pad to the next. Kermit the frog wishes to cross a river which has 3 lily pads. How many ways can Kermit cross a river which has
璀璨多彩的明珠—悉尼歌剧院 (2009-6-8) 大米星星 
发表于 2015-2-25 11:10