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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 6 |
| 4 | 126660 |
| 5 | 39205553940 |
| 6 | 72443102322181770 |
| 7 | 669339995480640046936115 |
| 8 | 26684517894223197491871690098160 |
| 9 | 4047051071271585783777915818898222938640 |
[0,0,6,126660,39205553940,72443102322181770, 669339995480640046936115, 26684517894223197491871690098160, 4047051071271585783777915818898222938640] |