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| n | a(n) |
|---|---|
| 0 | 3 |
| 1 | 12 |
| 2 | 120 |
| 3 | 360 |
| 4 | 1008 |
| 5 | 20160 |
| 6 | 259200 |
| 7 | 907200 |
| 8 | 6652800 |
| 9 | 19160064 |
| 10 | 39626496000 |
| 11 | 62270208000 |
| 12 | 603542016000 |
| 13 | 640493568000 |
| 14 | 1067062284288000 |
| 15 | 4001483566080000 |
| 16 | 4174096582656000 |
| 17 | 162193467211776000 |
| 18 | 13651830701752320000 |
| 19 | 481714597618974720000 |
[3,12,120,360,1008,20160,259200,907200,6652800, 19160064,39626496000,62270208000,603542016000, 640493568000,1067062284288000,4001483566080000, 4174096582656000,162193467211776000, 13651830701752320000,481714597618974720000] |