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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 28 |
| 4 | 364 |
| 5 | 9100 |
| 6 | 445900 |
| 7 | 43252300 |
| 8 | 8347693900 |
| 9 | 3213862151500 |
| 10 | 2471459994503500 |
| 11 | 3798634011551879500 |
| 12 | 11673202317498925703500 |
[1,4,28,364,9100,445900,43252300,8347693900, 3213862151500,2471459994503500, 3798634011551879500,11673202317498925703500] |