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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 15 |
| 2 | 330 |
| 3 | 9570 |
| 4 | 344520 |
| 5 | 14814360 |
| 6 | 740718000 |
| 7 | 42220926000 |
| 8 | 2702139264000 |
| 9 | 191851887744000 |
| 10 | 14964447244032000 |
| 11 | 1271978015742720000 |
| 12 | 117021977448330240000 |
| 13 | 11585175767384693760000 |
[1,15,330,9570,344520,14814360,740718000, 42220926000,2702139264000,191851887744000, 14964447244032000,1271978015742720000, 117021977448330240000,11585175767384693760000] |