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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 84 |
| 4 | 1168 |
| 5 | 20502 |
| 6 | 525796 |
| 7 | 18939708 |
| 8 | 802444170 |
| 9 | 38934305898 |
| 10 | 2170312156170 |
[1,6,84,1168,20502,525796,18939708,802444170, 38934305898,2170312156170] |