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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 25 |
| 5 | 99 |
| 6 | 416 |
| 7 | 1854 |
| 8 | 8411 |
| 9 | 38980 |
| 10 | 182829 |
| 11 | 867096 |
| 12 | 4145168 |
| 13 | 19955321 |
| 14 | 96619260 |
| 15 | 470157772 |
[1,2,7,25,99,416,1854,8411,38980,182829,867096, 4145168,19955321,96619260,470157772] |