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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 25 |
| 6 | 1227 |
| 7 | 84672 |
| 8 | 7635120 |
| 9 | 850626360 |
| 10 | 112876089480 |
| 11 | 17381709797760 |
| 12 | 3046480841900160 |
| 13 | 598731545755324800 |
| 14 | 130389773403373545600 |
| 15 | 31163616486434838067200 |
| 16 | 8109213009296586130944000 |
| 17 | 2282014010657773764160588800 |
| 18 | 690521215428258768326957184000 |
[1,25,1227,84672,7635120,850626360,112876089480, 17381709797760,3046480841900160, 598731545755324800,130389773403373545600, 31163616486434838067200,8109213009296586130944000, 2282014010657773764160588800, 690521215428258768326957184000] |