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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 32 |
| 3 | 360 |
| 4 | 4964 |
| 5 | 78064 |
| 6 | 1344020 |
| 7 | 24708928 |
| 8 | 477282794 |
| 9 | 9580852360 |
| 10 | 198322047840 |
| 11 | 4209371498256 |
| 12 | 91221481924426 |
| 13 | 2011834246746792 |
| 14 | 45039165331725264 |
| 15 | 1021419638492387856 |
| 16 | 23426910170090512779 |
| 17 | 542666070296546760492 |
| 18 | 12681393784980089971368 |
[1,4,32,360,4964,78064,1344020,24708928,477282794, 9580852360,198322047840,4209371498256, 91221481924426,2011834246746792,45039165331725264, 1021419638492387856,23426910170090512779, 542666070296546760492,12681393784980089971368] |