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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 4 |
| 4 | 112 |
| 5 | 6656 |
| 6 | 580796 |
| 7 | 159104356 |
| 8 | 100746278612 |
| 9 | 155176061188544 |
| 10 | 611605792148765530 |
[0,2,4,112,6656,580796,159104356,100746278612, 155176061188544,611605792148765530] |