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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 8 |
| 4 | 48 |
| 5 | 352 |
| 6 | 2880 |
| 7 | 25216 |
| 8 | 231168 |
| 9 | 2190848 |
| 10 | 21292032 |
| 11 | 211044352 |
| 12 | 2125246464 |
| 13 | 21681954816 |
| 14 | 223623069696 |
| 15 | 2327818174464 |
| 16 | 24424842461184 |
| 17 | 258054752698368 |
| 18 | 2742964283768832 |
| 19 | 29312424612462592 |
| 20 | 314739971287154688 |
| 21 | 3393951437605044224 |
| 22 | 36739207546043105280 |
[1,1,2,8,48,352,2880,25216,231168,2190848, 21292032,211044352,2125246464,21681954816, 223623069696,2327818174464,24424842461184, 258054752698368,2742964283768832, 29312424612462592,314739971287154688, 3393951437605044224,36739207546043105280] |