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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 20 |
| 3 | 6040 |
| 4 | 1824060 |
| 5 | 550860080 |
| 6 | 166357920100 |
| 7 | 50239541010120 |
| 8 | 15172175027136140 |
| 9 | 4581946618654104160 |
| 10 | 1383732706658512320180 |
| 11 | 417882695464252066590200 |
| 12 | 126199190297497465597920220 |
[0,20,6040,1824060,550860080,166357920100, 50239541010120,15172175027136140, 4581946618654104160,1383732706658512320180, 417882695464252066590200, 126199190297497465597920220] |