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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 168 |
| 5 | 130560 |
| 6 | 2778096640 |
| 7 | 2182547233161216 |
| 8 | 80604526437978334298112 |
| 9 | 171350523619928085051880067039232 |
| 10 | 24958704994164739282319189442326176511033344 |
[1,1,4,168,130560,2778096640,2182547233161216, 80604526437978334298112, 171350523619928085051880067039232, 24958704994164739282319189442326176511033344] |