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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | 0 |
| 2 | 8 |
| 3 | 56 |
| 4 | 304 |
| 5 | 1496 |
| 6 | 6992 |
| 7 | 31664 |
| 8 | 140384 |
| 9 | 613016 |
| 10 | 2646544 |
| 11 | 11325200 |
| 12 | 48122528 |
| 13 | 203306736 |
| 14 | 854829344 |
| 15 | 3579783776 |
| 16 | 14939605184 |
| 17 | 62162742296 |
| 18 | 257985394064 |
| 19 | 1068242117456 |
| 20 | 4414349525024 |
| 21 | 18208784215376 |
| 22 | 74988168359264 |
| 23 | 308369069291936 |
[-1,0,8,56,304,1496,6992,31664,140384,613016, 2646544,11325200,48122528,203306736,854829344, 3579783776,14939605184,62162742296,257985394064, 1068242117456,4414349525024,18208784215376, 74988168359264,308369069291936] |