三角形开始:
2;
2, 2;
2, 4, 2;
2, 6, 6, 2;
2, 8, 12, 8, 2;
2, 10, 20, 20, 10, 2;
2, 12, 30, 40, 30, 12, 2;
2, 14, 42, 70, 70, 42, 14, 2;
2, 16, 56, 112, 140, 112, 56, 16, 2;
2, 18, 72, 168, 252, 252, 168, 72, 18, 2;
2, 20, 90, 240, 420, 504, 420, 240, 90, 20, 2;
2, 22, 110, 330, 660, 924, 924, 660, 330, 110, 22, 2;
2, 24, 132, 440, 990, 1584, 1848, 1584, 990, 440, 132, 24, 2;