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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 9 |
| 6 | 30 |
| 7 | 103 |
| 8 | 435 |
| 9 | 2469 |
| 10 | 18958 |
| 11 | 194091 |
| 12 | 2661243 |
| 13 | 49287232 |
| 14 | 1236661032 |
[0,0,0,2,9,30,103,435,2469,18958,194091,2661243, 49287232,1236661032] |