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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 6 |
| 6 | 27 |
| 7 | 99 |
| 8 | 462 |
| 9 | 2205 |
| 10 | 11414 |
| 11 | 61028 |
| 12 | 337089 |
| 13 | 1894854 |
| 14 | 10794718 |
| 15 | 61989059 |
| 16 | 357903580 |
| 17 | 2073376576 |
| 18 | 12037807836 |
[1,1,1,3,6,27,99,462,2205,11414,61028,337089, 1894854,10794718,61989059,357903580,2073376576, 12037807836] |