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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 600 |
| 6 | 7920 |
| 7 | 108360 |
| 8 | 1693440 |
| 9 | 32114880 |
| 10 | 715478400 |
| 11 | 17616614400 |
| 12 | 467505561600 |
| 13 | 13438170345600 |
| 14 | 421361740800000 |
| 15 | 14345678194848000 |
| 16 | 524464774215782400 |
| 17 | 20420391682852761600 |
| 18 | 844038690729589555200 |
| 19 | 36981569420732192256000 |
[1,1,2,6,48,600,7920,108360,1693440,32114880, 715478400,17616614400,467505561600,13438170345600, 421361740800000,14345678194848000, 524464774215782400,20420391682852761600, 844038690729589555200,36981569420732192256000] |