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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 60 |
| 4 | 900 |
| 5 | 18945 |
| 6 | 536046 |
| 7 | 19750864 |
| 8 | 923023368 |
| 9 | 53456736825 |
| 10 | 3758407535410 |
| 11 | 315059660550756 |
| 12 | 31005946105301388 |
| 13 | 3535337355213234025 |
| 14 | 461813139285801522870 |
| 15 | 68448013078470849802560 |
| 16 | 11415281142784979557384208 |
| 17 | 2126537819755999634260404945 |
[1,1,6,60,900,18945,536046,19750864,923023368, 53456736825,3758407535410,315059660550756, 31005946105301388,3535337355213234025, 461813139285801522870,68448013078470849802560, 11415281142784979557384208, 2126537819755999634260404945] |