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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 12 |
| 6 | 60 |
| 7 | 180 |
| 8 | 630 |
| 9 | 10080 |
| 10 | 18144 |
| 11 | 453600 |
| 12 | 2494800 |
| 13 | 59875200 |
| 14 | 778377600 |
| 15 | 1089728640 |
| 16 | 40864824000 |
| 17 | 1307674368000 |
| 18 | 22230464256000 |
| 19 | 15390321408000 |
| 20 | 380140938777600 |
| 21 | 76028187755520000 |
| 22 | 1596591942865920000 |
[1,1,1,3,12,60,180,630,10080,18144,453600,2494800, 59875200,778377600,1089728640,40864824000, 1307674368000,22230464256000,15390321408000, 380140938777600,76028187755520000, 1596591942865920000] |