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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 30 |
| 4 | 180 |
| 5 | 1075 |
| 6 | 6366 |
| 7 | 37520 |
| 8 | 220500 |
| 9 | 1293615 |
| 10 | 7581240 |
| 11 | 44398387 |
[1,5,30,180,1075,6366,37520,220500,1293615, 7581240,44398387] |