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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 15 |
| 3 | 189 |
| 4 | 2352 |
| 5 | 29700 |
| 6 | 382239 |
| 7 | 5010005 |
| 8 | 66745536 |
| 9 | 901995588 |
| 10 | 12342120700 |
| 11 | 170724392916 |
| 12 | 2384209771200 |
| 13 | 33577620944400 |
| 14 | 476432168185575 |
| 15 | 6805332732133125 |
| 16 | 97790670976838400 |
| 17 | 1412830549632694500 |
| 18 | 20511953010895707900 |
| 19 | 299127910705042547700 |
| 20 | 4379986989467851320000 |
[1,15,189,2352,29700,382239,5010005,66745536, 901995588,12342120700,170724392916,2384209771200, 33577620944400,476432168185575,6805332732133125, 97790670976838400,1412830549632694500, 20511953010895707900,299127910705042547700, 4379986989467851320000] |