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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 121 |
| 6 | 721 |
| 7 | 5042 |
| 8 | 40326 |
| 9 | 362904 |
| 10 | 3628921 |
| 11 | 39917521 |
| 12 | 479006642 |
| 13 | 6227061126 |
| 14 | 87178654104 |
| 15 | 1307677996921 |
| 16 | 20922829805521 |
| 17 | 355687907102642 |
| 18 | 6402379932789126 |
| 19 | 121645187587486104 |
| 20 | 2432903315854636921 |
| 21 | 51090963094539245521 |
| 22 | 1124001083465514782642 |
[1,1,2,6,24,121,721,5042,40326,362904,3628921, 39917521,479006642,6227061126,87178654104, 1307677996921,20922829805521,355687907102642, 6402379932789126,121645187587486104, 2432903315854636921,51090963094539245521, 1124001083465514782642] |