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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 252 |
| 3 | 8864856 |
| 4 | 40638618022744 |
| 5 | 23098236228791472696480 |
| 6 | 1568841035670687222903484318855680 |
| 7 | 12397389650957442295025809189993580551236444160 |
[1,252,8864856,40638618022744, 23098236228791472696480, 1568841035670687222903484318855680, 12397389650957442295025809189993580551236444160] |