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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 4 |
| 3 | 6 |
| 4 | 96 |
| 5 | 480 |
| 6 | 6480 |
| 7 | 60480 |
| 8 | 887040 |
| 9 | 11975040 |
| 10 | 203212800 |
| 11 | 3512678400 |
| 12 | 69455232000 |
| 13 | 1444668825600 |
| 14 | 32953394073600 |
| 15 | 796373690112000 |
| 16 | 20671716409344000 |
| 17 | 567677135241216000 |
| 18 | 16550136029306880000 |
[1,0,4,6,96,480,6480,60480,887040,11975040, 203212800,3512678400,69455232000,1444668825600, 32953394073600,796373690112000,20671716409344000, 567677135241216000,16550136029306880000] |