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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 94 |
| 4 | 4480 |
| 5 | 332680 |
| 6 | 44019800 |
| 7 | 10480204080 |
| 8 | 3225666791760 |
| 9 | 1530272351292180 |
[1,5,94,4480,332680,44019800,10480204080, 3225666791760,1530272351292180] |