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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 6 | 6 |
| 7 | 8 |
| 8 | 16 |
| 9 | 60 |
| 10 | 440 |
| 11 | 6028 |
| 12 | 144672 |
| 13 | 5726600 |
| 14 | 355049200 |
| 15 | 33019575600 |
| 16 | 4442233570720 |
| 17 | 838471586473400 |
| 18 | 216325669310137200 |
| 19 | 74596301633778977800 |
| 20 | 33717528338468097965600 |
| 21 | 19638774380740743660063720 |
[1,2,3,4,5,6,8,16,60,440,6028,144672,5726600, 355049200,33019575600,4442233570720, 838471586473400,216325669310137200, 74596301633778977800,33717528338468097965600, 19638774380740743660063720] |