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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 28 |
| 6 | 121 |
| 7 | 587 |
| 8 | 3205 |
| 9 | 19201 |
| 10 | 123684 |
| 11 | 850873 |
| 12 | 6248839 |
| 13 | 48948805 |
| 14 | 407666212 |
| 15 | 3594074850 |
| 16 | 33405529547 |
| 17 | 326310068618 |
| 18 | 3342124657507 |
| 19 | 35827145094057 |
| 20 | 401325346421766 |
| 21 | 4689964771177970 |
| 22 | 57081316456694665 |
| 23 | 722295766109273335 |
| 24 | 9486188532177356598 |
[1,0,1,2,7,28,121,587,3205,19201,123684,850873, 6248839,48948805,407666212,3594074850,33405529547, 326310068618,3342124657507,35827145094057, 401325346421766,4689964771177970, 57081316456694665,722295766109273335, 9486188532177356598] |