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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 15 |
| 6 | 58 |
| 7 | 272 |
| 8 | 1614 |
| 9 | 11911 |
| 10 | 109539 |
| 11 | 1247691 |
| 12 | 17566431 |
| 13 | 305310547 |
| 14 | 6558690953 |
| 15 | 174688164414 |
[1,1,2,5,15,58,272,1614,11911,109539,1247691, 17566431,305310547,6558690953,174688164414] |