| crossing | alternative | non-alternative | total |
| 3 | 1 | 1 | |
| 4 | 1 | 1 | |
| 5 | 2 | 2 | |
| 6 | 3 | 3 | |
| 7 | 7 | 7 | |
| 8 | 18 | 3 | 21 |
| 9 | 41 | 8 | 49 |
| 10 | 123 | 42 | 165 |
| 11 | 367 | 185 | 552 |
| 12 | 1288 | 888 | 2176 |
| 13 | 4878 | 5110 | 9988 |
| 14 | 19536 | 27436 | 46972 |
| 15 | 85263 | 168030 | 253293 |
| 16 | 379799 | 1008906 | 1388705 |
| 17 | 1769979 | ? < 7413688 | |
| 18 | 8400285 | ? < 49128005 | |
| 19 | 40619385 | ||
| 20 | 199631989 | ||
| 21 | 990623857 |