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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 22 |
| 6 | 116 |
| 7 | 751 |
| 8 | 5629 |
| 9 | 47812 |
| 10 | 454000 |
| 11 | 4765191 |
| 12 | 54782415 |
| 13 | 684597511 |
| 14 | 9239952803 |
| 15 | 133952757202 |
| 16 | 2075907567337 |
| 17 | 34247231626810 |
| 18 | 599244998013964 |
| 19 | 11084682598687313 |
| 20 | 216127622080213322 |
[1,1,1,2,5,22,116,751,5629,47812,454000,4765191, 54782415,684597511,9239952803,133952757202, 2075907567337,34247231626810,599244998013964, 11084682598687313,216127622080213322] |