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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 58 |
| 5 | 333 |
| 6 | 2268 |
| 7 | 18281 |
| 8 | 173127 |
| 9 | 1905500 |
| 10 | 24080964 |
| 11 | 345381551 |
| 12 | 5563259860 |
| 13 | 99716732043 |
| 14 | 1973012968122 |
| 15 | 42792555114812 |
| 16 | 1011125250589597 |
| 17 | 25886430637780776 |
| 18 | 714600877541340733 |
| 19 | 21178498962170286988 |
[1,1,3,12,58,333,2268,18281,173127,1905500, 24080964,345381551,5563259860,99716732043, 1973012968122,42792555114812,1011125250589597, 25886430637780776,714600877541340733, 21178498962170286988] |