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| n | a(n) |
|---|---|
| 2 | 18 |
| 3 | 1800 |
| 4 | 352800 |
| 5 | 114307200 |
| 6 | 55324684800 |
| 7 | 37399486924800 |
| 8 | 33659538232320000 |
| 9 | 38910426196561920000 |
| 10 | 56186655427835412480000 |
| 11 | 99113260174701667614720000 |
| 12 | 209723658529668728672747520000 |
| 13 | 524309146324171821681868800000000 |
[18,1800,352800,114307200,55324684800, 37399486924800,33659538232320000, 38910426196561920000,56186655427835412480000, 99113260174701667614720000, 209723658529668728672747520000, 524309146324171821681868800000000] |