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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 36 |
| 4 | 288 |
| 5 | 7200 |
| 6 | 259200 |
| 7 | 12700800 |
| 8 | 203212800 |
| 9 | 5486745600 |
| 10 | 548674560000 |
| 11 | 66389621760000 |
| 12 | 4780052766720000 |
| 13 | 807828917575680000 |
| 14 | 158334467844833280000 |
| 15 | 35625255265087488000000 |
| 16 | 1140008168482799616000000 |
| 17 | 329462360691529089024000000 |
[1,1,4,36,288,7200,259200,12700800,203212800, 5486745600,548674560000,66389621760000, 4780052766720000,807828917575680000, 158334467844833280000,35625255265087488000000, 1140008168482799616000000, 329462360691529089024000000] |