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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5040 |
| 8 | 40320 |
| 9 | 362880 |
| 10 | 3628800 |
| 11 | 39191040 |
| 12 | 450293760 |
| 13 | 5534403840 |
| 14 | 72864645120 |
| 15 | 1026562867200 |
| 16 | 15441868062720 |
| 17 | 247319592468480 |
| 18 | 4205303137566720 |
| 19 | 75695456476200960 |
| 20 | 1438421245702963200 |
| 21 | 28616864514850160640 |
[1,1,2,6,24,120,720,5040,40320,362880,3628800, 39191040,450293760,5534403840,72864645120, 1026562867200,15441868062720,247319592468480, 4205303137566720,75695456476200960, 1438421245702963200,28616864514850160640] |