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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 8 |
| 5 | 21 |
| 6 | 48 |
| 7 | 377 |
| 8 | 1728 |
| 9 | 13129 |
| 10 | 61184 |
| 11 | 537965 |
| 12 | 3107840 |
| 13 | 34399197 |
| 14 | 235484928 |
| 15 | 2946509729 |
| 16 | 22794670080 |
| 17 | 323564702737 |
| 18 | 2824580218880 |
| 19 | 44888950379477 |
| 20 | 435346731352064 |
| 21 | 7640931012615717 |
| 22 | 81496599519363072 |
[0,1,2,5,8,21,48,377,1728,13129,61184,537965, 3107840,34399197,235484928,2946509729,22794670080, 323564702737,2824580218880,44888950379477, 435346731352064,7640931012615717, 81496599519363072] |