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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 6 |
| 3 | 72 |
| 4 | 1332 |
| 5 | 33264 |
| 6 | 1040256 |
| 7 | 38926656 |
| 8 | 1692061488 |
| 9 | 83688313536 |
| 10 | 4638320578944 |
| 11 | 284692939944192 |
| 12 | 19169186341398912 |
| 13 | 1404935464314299904 |
| 14 | 111348880778746460160 |
| 15 | 9489756817594314049536 |
| 16 | 865470841829802331976448 |
[1,1,6,72,1332,33264,1040256,38926656,1692061488, 83688313536,4638320578944,284692939944192, 19169186341398912,1404935464314299904, 111348880778746460160,9489756817594314049536, 865470841829802331976448] |