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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 65 |
| 5 | 856 |
| 6 | 17497 |
| 7 | 554632 |
| 8 | 29533905 |
| 9 | 2782465840 |
| 10 | 486675409841 |
| 11 | 167183253706624 |
[1,1,3,10,65,856,17497,554632,29533905,2782465840, 486675409841,167183253706624] |