题目:一列数1,7,2,14,3,21,……其中,第13个数是多少?第14个数呢?【分析与解】观察这一列数,前6个已知数的排列很有规律,这个规律是:每两个数之间是乘积关系,后一个数都是前一个数的7倍。把每两个数作为一组,它们的关系为:第1组:1和7,7的1倍是7(7×1=7);第2组:2和14,7的2倍是14(7×2=14);第3组:3和21,7的3倍是21(7×3=21); Title: a number of 1,7,2,14,3,21, ... ... Among them, the 13th number is how much? The 14th number? [Analytical and Settlement] to observe the number of columns, the first six known The arrangement is very regular, the law is: every two numbers is the product of the relationship between the latter number is seven times the previous number. Each two numbers are grouped together as follows: Group 1: 1 times 1 and 7, 7 is 7 (7 × 1 = 7); Group 2: 2 times 2 and 14, 7 is 14 (7 × 2 = 14); Group 3: 3 times 21 for 3 and 21,7 (7 × 3 = 21);