本帖最后由 王守恩 于 2019-4-27 16:41 编辑
主帖:在方程 x+y+z=19 的正整数解中,满足任一数皆小于另两数之和的解 (x,y,z) 有几组?
等同于:三条边都是整数的三角形计数问题,
我们设三角形周长为整数 n,n = 0,1,2,3,4,5,6,7,8,......
对应三角形的个数是 S(n),则有如下数字串:
0, 0, 0, 1, 0, 1, 1, 2, 1, 3, 2, 4, 3, 5, 4, 7, 5, 8, 7, 10, 8,
12, 10, 14, 12, 16, 14, 19, 16, 21, 19, 24, 21, 27, 24, 30,
27, 33, 30, 37, 33, 40, 37, 44, 40, 48, 44, 52, 48, 56, 52,
61, 56, 65, 61, 70, 65, 75, 70, 80, 75, 85, 80, 91, 85, 96,
91, 102, 96, 108, 102, 114, 108, 120, 114, 127, 120, 133,
127, 140, 133, 147, 140, 154, 147, 161, 154, ............ |