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| n | a(n) |
|---|---|
| 4 | 0 |
| 5 | 400 |
| 6 | 13280 |
| 7 | 278880 |
| 8 | 5120640 |
| 9 | 90518400 |
| 10 | 1602720000 |
| 11 | 28966291200 |
| 12 | 539568691200 |
| 13 | 10411578777600 |
| 14 | 208646710272000 |
| 15 | 4347290787840000 |
| 16 | 94201374339072000 |
| 17 | 2122386883448832000 |
| 18 | 49691667829579776000 |
| 19 | 1208138588893716480000 |
| 20 | 30476152489092710400000 |
| 21 | 796939223079733493760000 |
[0,400,13280,278880,5120640,90518400,1602720000, 28966291200,539568691200,10411578777600, 208646710272000,4347290787840000, 94201374339072000,2122386883448832000, 49691667829579776000,1208138588893716480000, 30476152489092710400000,796939223079733493760000] |