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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 272 |
| 5 | 7424 |
| 6 | 405504 |
| 7 | 44302336 |
| 8 | 9680453632 |
| 9 | 4230542786560 |
| 10 | 3697657604210688 |
| 11 | 6463791365183504384 |
| 12 | 22598414411798807576576 |
| 13 | 158015104883301198495481856 |
| 14 | 2209780998563745292895322636288 |
[1,1,3,20,272,7424,405504,44302336,9680453632, 4230542786560,3697657604210688, 6463791365183504384,22598414411798807576576, 158015104883301198495481856, 2209780998563745292895322636288] |