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| n | a(n) |
|---|---|
| 4 | 1 |
| 5 | 20 |
| 6 | 375 |
| 7 | 7560 |
| 8 | 167825 |
| 9 | 4110120 |
| 10 | 110602800 |
| 11 | 3252075750 |
| 12 | 103881924300 |
| 13 | 3585467886000 |
| 14 | 133052005386300 |
| 15 | 5284678706307000 |
| 16 | 223761183682286250 |
| 17 | 10063370411081988000 |
| 18 | 479152851159102120000 |
| 19 | 24082014064135799772000 |
[1,20,375,7560,167825,4110120,110602800, 3252075750,103881924300,3585467886000, 133052005386300,5284678706307000, 223761183682286250,10063370411081988000, 479152851159102120000,24082014064135799772000] |