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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 5 |
| 4 | 91 |
| 5 | 40727 |
| 6 | 20874574 |
| 7 | 23274835718 |
| 8 | 39868129982498 |
| 9 | 102457584348682968 |
[1,0,5,91,40727,20874574,23274835718, 39868129982498,102457584348682968] |