弱弱问一句,什么叫triangular numbers ? -- by 会员 neverlandlin (2011/2/14 21:50:00)
http://en.wikipedia.org/wiki/Triangular_number
A triangular number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangle number. The nth triangle number is the number of dots in a triangle with n dots on a side. A triangle number is, equivalently, the sum of the nnatural numbers from 1 to n. |