T(4,1)=6,因为我们有u(ud)dudud、udu。
三角形开始:
1;
1, 1;
2, 2, 1;
4, 6, 3, 1;
9, 16, 12, 4, 1;
21, 45, 40, 20, 5, 1;
51, 126, 135, 80, 30, 6, 1;
127, 357, 441, 315, 140, 42, 7, 1;
323, 1016, 1428, 1176, 630, 224, 56, 8, 1;
835, 2907, 4572, 4284, 2646, 1134, 336, 72, 9, 1;
...