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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 18 |
| 6 | 86 |
| 7 | 549 |
| 8 | 4647 |
| 9 | 52060 |
| 10 | 772976 |
| 11 | 15240116 |
| 12 | 400345371 |
| 13 | 14063594530 |
| 14 | 663256392496 |
| 15 | 42161077371566 |
| 16 | 3625838175218123 |
| 17 | 423372648479289300 |
| 18 | 67333725775723184308 |
| 19 | 14628921614102655999804 |
| 20 | 4352732830667872529962044 |
[1,1,1,2,5,18,86,549,4647,52060,772976,15240116, 400345371,14063594530,663256392496,42161077371566, 3625838175218123,423372648479289300, 67333725775723184308,14628921614102655999804, 4352732830667872529962044] |