题目

Life in the future will be different from life today. Between then and now many changes will happen. But what will the changes be?The population is growing fast. There will be many people in the world and most of them will live longer than people live now.Computers will be much smaller and more useful，and there will be at least one in every home. And computer studies will be one of the important subjects in schools then. People will work fewer hours than they do now and they will have more free time for sports，watching TV and traveling. Traveling will be much cheaper and easier. And many m将全体正整数排成一个三角形数阵12       34       5      67       8      9      1011      12     13     14      15…　…　…　…　…　…　…　…　…根据以上排列规律，数阵中第行的从左至右的第个数是              .