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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 20 |
| 2 | 336 |
| 3 | 5440 |
| 4 | 87296 |
| 5 | 1397760 |
| 6 | 22368256 |
| 7 | 357908480 |
| 8 | 5726601216 |
| 9 | 91625881600 |
| 10 | 1466015154176 |
| 11 | 23456246661120 |
| 12 | 375299963355136 |
| 13 | 6004799480791040 |
| 14 | 96076791961092096 |
| 15 | 1537228672451215360 |
| 16 | 24595658763514413056 |
| 17 | 393530540233410478080 |
| 18 | 6296488643803287126016 |
[1,20,336,5440,87296,1397760,22368256,357908480, 5726601216,91625881600,1466015154176, 23456246661120,375299963355136,6004799480791040, 96076791961092096,1537228672451215360, 24595658763514413056,393530540233410478080, 6296488643803287126016] |