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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 48 |
| 4 | 504 |
| 5 | 6600 |
| 6 | 103680 |
| 7 | 1900080 |
| 8 | 39795840 |
| 9 | 937681920 |
| 10 | 24548832000 |
| 11 | 706966444800 |
| 12 | 22210346188800 |
| 13 | 755916735974400 |
| 14 | 27706219904563200 |
| 15 | 1088037381150720000 |
| 16 | 45576301518139392000 |
| 17 | 2028445209752113152000 |
| 18 | 95589693062063456256000 |
| 19 | 4754884242802394308608000 |
[1,1,6,48,504,6600,103680,1900080,39795840, 937681920,24548832000,706966444800,22210346188800, 755916735974400,27706219904563200, 1088037381150720000,45576301518139392000, 2028445209752113152000,95589693062063456256000, 4754884242802394308608000] |