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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 147456 |
| 9 | 3265920 |
| 10 | 129024000 |
| 11 | 1097712000 |
| 12 | 12939264000 |
| 13 | 66784798080 |
| 14 | 436483031040 |
| 15 | 1669619952000 |
| 16 | 7629571031040 |
| 17 | 23828156352000 |
| 18 | 85476013572096 |
| 19 | 230333593351680 |
| 20 | 693478195200000 |
| 21 | 1669577821632000 |
[0,0,0,0,0,0,0,147456,3265920,129024000, 1097712000,12939264000,66784798080,436483031040, 1669619952000,7629571031040,23828156352000, 85476013572096,230333593351680,693478195200000, 1669577821632000] |