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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 144 |
| 7 | 5040 |
| 8 | 40320 |
| 9 | 362880 |
| 10 | 725760 |
| 11 | 39916800 |
| 12 | 479001600 |
| 13 | 6227020800 |
| 14 | 17435658240 |
| 15 | 1307674368000 |
| 16 | 20922789888000 |
| 17 | 355687428096000 |
| 18 | 1280474741145600 |
| 19 | 850665037824000 |
| 20 | 221172909834240000 |
[1,1,2,6,24,120,144,5040,40320,362880,725760, 39916800,479001600,6227020800,17435658240, 1307674368000,20922789888000,355687428096000, 1280474741145600,850665037824000, 221172909834240000] |