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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 15 |
| 3 | 336 |
| 4 | 8880 |
| 5 | 254596 |
| 6 | 7606446 |
| 7 | 231899522 |
| 8 | 7137539256 |
| 9 | 220623286632 |
| 10 | 6831984816402 |
| 11 | 211719998195278 |
| 12 | 6562887569336652 |
| 13 | 203453536535818388 |
| 14 | 6307290799931347878 |
| 15 | 195532244201392935354 |
| 16 | 6061637498660735815968 |
[0,1,15,336,8880,254596,7606446,231899522, 7137539256,220623286632,6831984816402, 211719998195278,6562887569336652, 203453536535818388,6307290799931347878, 195532244201392935354,6061637498660735815968] |