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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 48 |
| 5 | 480 |
| 6 | 5040 |
| 7 | 57960 |
| 8 | 806400 |
| 9 | 13426560 |
| 10 | 250992000 |
| 11 | 5102697600 |
| 12 | 113283878400 |
| 13 | 2760905347200 |
| 14 | 73287883468800 |
| 15 | 2093750122464000 |
| 16 | 63947194517606400 |
| 17 | 2082970788291993600 |
| 18 | 72182922107859763200 |
| 19 | 2651026034089585152000 |
[1,1,2,6,48,480,5040,57960,806400,13426560, 250992000,5102697600,113283878400,2760905347200, 73287883468800,2093750122464000,63947194517606400, 2082970788291993600,72182922107859763200, 2651026034089585152000] |