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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 42 |
| 5 | 310 |
| 6 | 1965 |
| 7 | 12621 |
| 8 | 86828 |
| 9 | 614664 |
| 10 | 4137255 |
| 11 | 24696507 |
| 12 | 135776850 |
| 13 | 704076594 |
| 14 | 3499379975 |
| 15 | 16814719845 |
| 16 | 78438871176 |
| 17 | 355384933088 |
| 18 | 1560604589541 |
| 19 | 6638708644299 |
| 20 | 27407266803082 |
| 21 | 110092581701214 |
| 22 | 431253742334877 |
[1,3,42,310,1965,12621,86828,614664,4137255, 24696507,135776850,704076594,3499379975, 16814719845,78438871176,355384933088, 1560604589541,6638708644299,27407266803082, 110092581701214,431253742334877] |