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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 33 |
| 5 | 180 |
| 6 | 1185 |
| 7 | 8890 |
| 8 | 79233 |
| 9 | 769608 |
| 10 | 8392065 |
| 11 | 97609358 |
| 12 | 1249180449 |
| 13 | 16946392892 |
| 14 | 249854555041 |
| 15 | 3881392411650 |
| 16 | 64853211006977 |
| 17 | 1135530767344144 |
| 18 | 21209811847666689 |
| 19 | 413312033834754966 |
[1,0,1,6,33,180,1185,8890,79233,769608,8392065, 97609358,1249180449,16946392892,249854555041, 3881392411650,64853211006977,1135530767344144, 21209811847666689,413312033834754966] |