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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 25 |
| 5 | 133 |
| 6 | 851 |
| 7 | 6313 |
| 8 | 53061 |
| 9 | 497493 |
| 10 | 5144500 |
| 11 | 58161126 |
| 12 | 713789847 |
| 13 | 9453038227 |
| 14 | 134405493652 |
| 15 | 2042529150110 |
| 16 | 33045300698761 |
| 17 | 567165849906233 |
| 18 | 10294218618819268 |
| 19 | 197022941365579804 |
| 20 | 3966001076798967837 |
[1,1,2,6,25,133,851,6313,53061,497493,5144500, 58161126,713789847,9453038227,134405493652, 2042529150110,33045300698761,567165849906233, 10294218618819268,197022941365579804, 3966001076798967837] |