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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 10 |
| 3 | 120 |
| 4 | 1620 |
| 5 | 23560 |
| 6 | 360352 |
| 7 | 5714800 |
| 8 | 93129840 |
| 9 | 1550132320 |
| 10 | 26242225600 |
| 11 | 450448137216 |
| 12 | 7821608426880 |
| 13 | 137145465358080 |
| 14 | 2424899712359680 |
| 15 | 43186456105340160 |
| 16 | 774013543036174080 |
| 17 | 13949937641606981120 |
| 18 | 252666943472167541760 |
| 19 | 4596736161565468815360 |
[1,1,10,120,1620,23560,360352,5714800,93129840, 1550132320,26242225600,450448137216,7821608426880, 137145465358080,2424899712359680, 43186456105340160,774013543036174080, 13949937641606981120,252666943472167541760, 4596736161565468815360] |