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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 124 |
| 4 | 1280 |
| 5 | 13456 |
| 6 | 143808 |
| 7 | 1556416 |
| 8 | 17006592 |
| 9 | 187207936 |
| 10 | 2072947712 |
| 11 | 23063919616 |
| 12 | 257634271232 |
| 13 | 2887544049664 |
| 14 | 32456082440192 |
| 15 | 365710391885824 |
| 16 | 4129672996585472 |
| 17 | 46721752249729024 |
| 18 | 529486122704437248 |
| 19 | 6009576477811277824 |
| 20 | 68299997524116111360 |
[1,12,124,1280,13456,143808,1556416,17006592, 187207936,2072947712,23063919616,257634271232, 2887544049664,32456082440192,365710391885824, 4129672996585472,46721752249729024, 529486122704437248,6009576477811277824, 68299997524116111360] |