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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 84 |
| 5 | 984 |
| 6 | 14640 |
| 7 | 262800 |
| 8 | 5513760 |
| 9 | 132289920 |
| 10 | 3571464960 |
| 11 | 107140320000 |
| 12 | 3535590643200 |
| 13 | 127280784153600 |
| 14 | 4963944354969600 |
| 15 | 208485575730432000 |
| 16 | 9381849600195072000 |
| 17 | 450328759886573568000 |
| 18 | 22966766398527823872000 |
| 19 | 1240205379118128783360000 |
[0,1,2,10,84,984,14640,262800,5513760,132289920, 3571464960,107140320000,3535590643200, 127280784153600,4963944354969600, 208485575730432000,9381849600195072000, 450328759886573568000,22966766398527823872000, 1240205379118128783360000] |