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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 1 |
| 7 | 3 |
| 8 | 13 |
| 9 | 37 |
| 10 | 67 |
| 11 | 147 |
| 12 | 499 |
| 13 | 1519 |
| 14 | 5231 |
| 15 | 22885 |
| 16 | 101333 |
| 17 | 548323 |
| 18 | 3012179 |
| 19 | 18194005 |
| 20 | 121163279 |
| 21 | 875290875 |
[1,1,1,1,1,1,3,13,37,67,147,499,1519,5231,22885, 101333,548323,3012179,18194005,121163279, 875290875] |