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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 15 |
| 6 | 122 |
| 7 | 990 |
| 8 | 9210 |
| 9 | 91013 |
| 10 | 1001285 |
| 11 | 11774254 |
| 12 | 150849588 |
| 13 | 2059781391 |
[0,0,0,2,15,122,990,9210,91013,1001285,11774254, 150849588,2059781391] |