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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 24 |
| 4 | 576 |
| 5 | 51840 |
| 6 | 13063680 |
| 7 | 9170703360 |
| 8 | 19808719257600 |
| 9 | 131569513308979200 |
| 10 | 2600339861038664908800 |
| 11 | 152915585868239728626892800 |
| 12 | 27051378802435080953011843891200 |
| 13 | 14395932257291877030764312963579904000 |
[1,4,24,576,51840,13063680,9170703360, 19808719257600,131569513308979200, 2600339861038664908800, 152915585868239728626892800, 27051378802435080953011843891200, 14395932257291877030764312963579904000] |