简单的最小二乘曲线拟合方法，供图形图像绘制参考使用。-Simple least-squares curve fitting method for graphics image rendering their use and reference.

写一个函数，求S=a+aa+aaa+aaaa+…..+aaa…aaaa(n个 a)中的第n项，通过调用计算S的值。 -Write a function, find S = a+ aa+ aaa+ aaaa+ ... ..+ aaa ... aaaa (n a a), the first n items, by calling the calculated S value.