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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 105 |
| 6 | 550 |
| 7 | 3228 |
| 8 | 20878 |
| 9 | 146994 |
| 10 | 1116000 |
| 11 | 9068288 |
| 12 | 78384726 |
| 13 | 717102126 |
| 14 | 6913783826 |
| 15 | 69991576572 |
[1,2,6,23,105,550,3228,20878,146994,1116000, 9068288,78384726,717102126,6913783826,69991576572] |