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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 28 |
| 5 | 167 |
| 6 | 810 |
| 7 | 4664 |
| 8 | 38344 |
| 9 | 207255 |
| 10 | 2059900 |
| 11 | 19385131 |
| 12 | 174417011 |
| 13 | 1922011637 |
| 14 | 21058799803 |
| 15 | 208257199434 |
| 16 | 2905150193223 |
| 17 | 38462668421772 |
| 18 | 481607876817202 |
| 19 | 7526871509864950 |
[1,1,3,8,28,167,810,4664,38344,207255,2059900, 19385131,174417011,1922011637,21058799803, 208257199434,2905150193223,38462668421772, 481607876817202,7526871509864950] |