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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 5 |
| 7 | 240 |
| 8 | 130 |
| 9 | 4095 |
| 10 | 884 |
| 11 | 122522400 |
| 12 | 5785 |
| 13 | 1570247078400 |
| 14 | 7050580 |
| 15 | 6402818331 |
| 16 | 55911099400 |
| 17 | 83044763560621070208000 |
| 18 | 2152604285 |
| 19 | 342696507457909818131702784000 |
| 20 | 122400523811956 |
| 21 | 16017296251646471425875 |
[1,1,1,2,6,5,240,130,4095,884,122522400,5785, 1570247078400,7050580,6402818331,55911099400, 83044763560621070208000,2152604285, 342696507457909818131702784000,122400523811956, 16017296251646471425875] |