在两千多年前,古希腊人就研究过形如S=(1+n)n/2(n∈N)的自然数,这就是所谓的三角数,它的最小的前几个是1,3,6,10,….显然,S=1+2+3+…+n,由此可知,除1以外的任何一个三角数,总可以分拆成多个连续自然数的和。这是三角数的一个有趣的性质。下面我们来考察数1990是否是一个三角数? 假设数1990是一个三角数,则有 1990=(k+1)+(k+2)+…+m Over 2,000 years ago, the ancient Greeks studied natural numbers of the form S=(1+n)n/2(n∈N). This is the so-called number of triangles. The first few of them are 1, 3,6,10,.... Obviously, S=1+2+3+...+n, it can be seen that any number of triangles other than 1 can be divided into a sum of a plurality of continuous natural numbers. This is an interesting property of the number of triangles. Let us examine whether the number 1990 is a triangle number. Assuming that the number 1990 is a triangle number, then 1990=(k+1)+(k+2)+...+m