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| n | a(n) |
|---|---|
| 1 | -1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 12 |
| 6 | 52 |
| 7 | 456 |
| 8 | 6873 |
| 9 | 191532 |
| 10 | 9733032 |
| 11 | 903753248 |
| 12 | 154108311046 |
| 13 | 48542114686912 |
| 14 | 28401423719121392 |
| 15 | 31021002160355166800 |
| 16 | 63530415842308265086523 |
| 17 | 244912778438520759443245824 |
| 18 | 1783398846284777975419599903948 |
| 19 | 24605641171260376770598003978281472 |
[-1,1,2,3,12,52,456,6873,191532,9733032,903753248, 154108311046,48542114686912,28401423719121392, 31021002160355166800,63530415842308265086523, 244912778438520759443245824, 1783398846284777975419599903948, 24605641171260376770598003978281472] |