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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 1 |
| 4 | 6 |
| 5 | 38 |
| 6 | 232 |
| 7 | 1607 |
| 8 | 12984 |
| 9 | 117513 |
| 10 | 1182540 |
| 11 | 13060248 |
| 12 | 157314056 |
| 13 | 2051314949 |
[1,1,6,38,232,1607,12984,117513,1182540,13060248, 157314056,2051314949] |