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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 0 |
| 4 | 2 |
| 5 | 4 |
| 6 | 19 |
| 7 | 84 |
| 8 | 821 |
| 9 | 12485 |
| 10 | 343572 |
| 11 | 16164685 |
| 12 | 1289300669 |
[0,2,0,2,4,19,84,821,12485,343572,16164685, 1289300669] |