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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 2 |
| 7 | 8 |
| 8 | 48 |
| 9 | 450 |
| 10 | 5752 |
| 11 | 90555 |
| 12 | 1612917 |
| 13 | 31297424 |
| 14 | 652159986 |
| 15 | 14499787794 |
| 16 | 342646826428 |
[0,0,0,0,0,1,2,8,48,450,5752,90555,1612917, 31297424,652159986,14499787794,342646826428] |