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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 480 |
| 7 | 3600 |
| 8 | 23040 |
| 9 | 221760 |
| 10 | 1895040 |
| 11 | 22176000 |
| 12 | 235791360 |
| 13 | 3242695680 |
| 14 | 41153495040 |
| 15 | 649729382400 |
| 16 | 9572600217600 |
| 17 | 170530956288000 |
| 18 | 2858960008396800 |
| 19 | 56707673547571200 |
| 20 | 1065538430749900800 |
| 21 | 23283629822509056000 |
| 22 | 484535856895701811200 |
[1,1,2,6,24,120,480,3600,23040,221760,1895040, 22176000,235791360,3242695680,41153495040, 649729382400,9572600217600,170530956288000, 2858960008396800,56707673547571200, 1065538430749900800,23283629822509056000, 484535856895701811200] |