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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 104 |
| 7 | 716 |
| 8 | 7624 |
| 9 | 122010 |
| 10 | 2946285 |
| 11 | 103833895 |
| 12 | 5187290899 |
[1,1,2,6,20,104,716,7624,122010,2946285,103833895, 5187290899] |