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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 48 |
| 4 | 336 |
| 5 | 2400 |
| 6 | 16752 |
| 7 | 117648 |
| 8 | 823200 |
| 9 | 5764752 |
| 10 | 40351200 |
| 11 | 282475248 |
| 12 | 1977309600 |
| 13 | 13841287200 |
| 14 | 96888892752 |
| 15 | 678223070400 |
| 16 | 4747560686400 |
| 17 | 33232930569600 |
| 18 | 232630508205648 |
| 19 | 1628413597910448 |
| 20 | 11398895145019200 |
| 21 | 79792266297494304 |
| 22 | 558545863800808752 |
[1,6,48,336,2400,16752,117648,823200,5764752, 40351200,282475248,1977309600,13841287200, 96888892752,678223070400,4747560686400, 33232930569600,232630508205648,1628413597910448, 11398895145019200,79792266297494304, 558545863800808752] |