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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 84 |
| 3 | 4432 |
| 4 | 432144 |
| 5 | 67336512 |
| 6 | 15330202432 |
| 7 | 4799825862912 |
| 8 | 1978228668612864 |
| 9 | 1038257514383795200 |
| 10 | 676117122084133770240 |
| 11 | 534973800492211106598912 |
| 12 | 505535479689176978173726720 |
[1,4,84,4432,432144,67336512,15330202432, 4799825862912,1978228668612864, 1038257514383795200,676117122084133770240, 534973800492211106598912, 505535479689176978173726720] |