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| n | a(n) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 2 |
| 6 | 11 |
| 7 | 75 |
| 8 | 740 |
| 9 | 10692 |
| 10 | 229068 |
| 11 | 7005022 |
| 12 | 305866545 |
| 13 | 18868736922 |
[0,0,0,2,11,75,740,10692,229068,7005022,305866545, 18868736922] |