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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 10 |
| 5 | 20 |
| 6 | 248 |
| 7 | 1072 |
| 8 | 31178 |
| 9 | 270026 |
| 10 | 18806964 |
| 11 | 329412610 |
| 12 | 54393195014 |
| 13 | 1931171930256 |
| 14 | 749416883107560 |
| 15 | 54217060622200086 |
[1,1,2,2,10,20,248,1072,31178,270026,18806964, 329412610,54393195014,1931171930256, 749416883107560,54217060622200086] |