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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 36 |
| 4 | 576 |
| 5 | 14400 |
| 6 | 518400 |
| 7 | 25401600 |
| 8 | 1625702400 |
| 9 | 131681894400 |
| 10 | 13168189440000 |
| 11 | 1593350922240000 |
| 12 | 229442532802560000 |
| 13 | 38775788043632640000 |
| 14 | 7600054456551997440000 |
| 15 | 1710012252724199424000000 |
| 16 | 437763136697395052544000000 |
| 17 | 126513546505547170185216000000 |
[1,1,4,36,576,14400,518400,25401600,1625702400, 131681894400,13168189440000,1593350922240000, 229442532802560000,38775788043632640000, 7600054456551997440000,1710012252724199424000000, 437763136697395052544000000, 126513546505547170185216000000] |