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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 4 |
| 5 | 4 |
| 6 | 15 |
| 7 | 22 |
| 8 | 68 |
| 9 | 131 |
| 10 | 376 |
| 11 | 892 |
| 12 | 2627 |
| 13 | 7217 |
| 14 | 22349 |
| 15 | 67271 |
| 16 | 229553 |
[0,1,1,4,4,15,22,68,131,376,892,2627,7217,22349, 67271,229553] |