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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 56 |
| 5 | 285 |
| 6 | 1533 |
| 7 | 8571 |
| 8 | 49311 |
| 9 | 290019 |
| 10 | 1735845 |
| 11 | 10538550 |
| 12 | 64741482 |
| 13 | 401708635 |
| 14 | 2513837901 |
| 15 | 15847466748 |
| 16 | 100547969532 |
| 17 | 641570954283 |
| 18 | 4114313131809 |
| 19 | 26503231512588 |
| 20 | 171416266008912 |
| 21 | 1112726163448431 |
| 22 | 7247066415484731 |
[1,1,3,12,56,285,1533,8571,49311,290019,1735845, 10538550,64741482,401708635,2513837901, 15847466748,100547969532,641570954283, 4114313131809,26503231512588,171416266008912, 1112726163448431,7247066415484731] |