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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 56 |
| 3 | 624 |
| 4 | 3288 |
| 5 | 16912 |
| 6 | 51864 |
| 7 | 164692 |
| 8 | 422792 |
| 9 | 1023416 |
| 10 | 2101272 |
| 11 | 4387296 |
| 12 | 8214688 |
| 13 | 15485996 |
[4,56,624,3288,16912,51864,164692,422792,1023416, 2101272,4387296,8214688,15485996] |