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| n | a(n) |
|---|---|
| 2 | 4 |
| 3 | 256 |
| 4 | 2048 |
| 5 | 4194304 |
| 6 | 54525952 |
| 7 | 134754598912 |
| 8 | 4797478469632 |
| 9 | 281474976710656 |
| 10 | 6757369765892718592 |
| 11 | 745800601892181508096 |
| 12 | 15816641891325181952 |
| 13 | 198634540185704451801088 |
[4,256,2048,4194304,54525952,134754598912, 4797478469632,281474976710656,6757369765892718592, 745800601892181508096,15816641891325181952, 198634540185704451801088] |