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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 2 |
| 7 | 11 |
| 8 | 62 |
| 9 | 408 |
| 10 | 3056 |
| 11 | 25821 |
| 12 | 242802 |
| 13 | 2517303 |
| 14 | 28540102 |
| 15 | 351383192 |
| 16 | 4669815008 |
| 17 | 66640974977 |
| 18 | 1016522211474 |
| 19 | 16507095990251 |
| 20 | 284343231536742 |
| 21 | 5178919228252440 |
[0,0,0,0,1,2,11,62,408,3056,25821,242802,2517303, 28540102,351383192,4669815008,66640974977, 1016522211474,16507095990251,284343231536742, 5178919228252440] |