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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 10 |
| 5 | 90 |
| 6 | 1260 |
| 7 | 167580 |
| 8 | 10345048560 |
| 9 | 210224307704851440 |
| 10 | 142378995493242911206243440 |
| 11 | 4409130655192711420325660927780160 |
| 12 | 308972448405145190275995459920449062174478109373358971999360 |
[1,1,1,2,10,90,1260,167580,10345048560, 210224307704851440,142378995493242911206243440, 4409130655192711420325660927780160, 30897244840514519027599545992044906217447810937335\ 8971999360] |