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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 12 |
| 4 | 120 |
| 5 | 168 |
| 6 | 1680 |
| 7 | 2217600 |
| 8 | 2620800 |
| 9 | 7539840 |
| 10 | 2459358720 |
| 11 | 45321292800 |
| 12 | 168289228800 |
| 13 | 3854798070733209600 |
| 14 | 7300628131494297600 |
| 15 | 72805439777469235200 |
| 16 | 1670428855291340390400 |
| 17 | 101997752596918507929600 |
| 18 | 292808914099957994618880000 |
[1,2,12,120,168,1680,2217600,2620800,7539840, 2459358720,45321292800,168289228800, 3854798070733209600,7300628131494297600, 72805439777469235200,1670428855291340390400, 101997752596918507929600, 292808914099957994618880000] |