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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 4 |
| 6 | 4 |
| 7 | 36 |
| 8 | 18 |
| 9 | 64 |
| 10 | 576 |
| 11 | 14400 |
| 12 | 43200 |
| 13 | 518400 |
| 14 | 518400 |
| 15 | 5080320 |
| 16 | 12700800 |
| 17 | 1625702400 |
| 18 | 1625702400 |
| 19 | 131681894400 |
| 20 | 131681894400 |
| 21 | 627056640000 |
| 22 | 13168189440000 |
| 23 | 1593350922240000 |
[1,1,1,1,1,4,4,36,18,64,576,14400,43200,518400, 518400,5080320,12700800,1625702400,1625702400, 131681894400,131681894400,627056640000, 13168189440000,1593350922240000] |