如果填后面的数:1/21/61/121/201/301/421/561/72如果求第n个数:第n个为1/n(n+1)或1/n-1/(n+1)如果求和:1/2+1/6+1/12+1/20+1/30+1/42=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7=1-1/7=6/7