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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 68 |
| 5 | 399 |
| 6 | 2531 |
| 7 | 16994 |
| 8 | 119199 |
| 9 | 865849 |
| 10 | 6474177 |
| 11 | 49616016 |
| 12 | 388484212 |
| 13 | 3100311228 |
| 14 | 25172981053 |
| 15 | 207665895001 |
| 16 | 1738775327319 |
| 17 | 14764815028481 |
| 18 | 127076945426555 |
| 19 | 1108103873824072 |
| 20 | 9787004793441886 |
| 21 | 87539719110388691 |
[1,1,3,13,68,399,2531,16994,119199,865849,6474177, 49616016,388484212,3100311228,25172981053, 207665895001,1738775327319,14764815028481, 127076945426555,1108103873824072,9787004793441886, 87539719110388691] |