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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 20 |
| 3 | 1680 |
| 4 | 369600 |
| 5 | 168168000 |
| 6 | 137225088000 |
| 7 | 182499151015439 |
| 8 | 369333660414653745 |
| 9 | 1080107104118231632500 |
| 10 | 4384231121059173932562000 |
| 11 | 23913914175434871142808715000 |
| 12 | 170693577054027116430454774306800 |
| 13 | 1559452501977701854639515593122328400 |
[1,1,20,1680,369600,168168000,137225088000, 182499151015439,369333660414653745, 1080107104118231632500,4384231121059173932562000, 23913914175434871142808715000, 170693577054027116430454774306800, 1559452501977701854639515593122328400] |