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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 119 |
| 6 | 708 |
| 7 | 4914 |
| 8 | 38976 |
| 9 | 347765 |
| 10 | 3447712 |
| 11 | 37598286 |
| 12 | 447294144 |
| 13 | 5764747515 |
| 14 | 80011430240 |
| 15 | 1189835682714 |
| 16 | 18873422539776 |
| 17 | 318085061976105 |
| 18 | 5676223254661760 |
| 19 | 106919460527212950 |
| 20 | 2119973556022047744 |
| 21 | 44136046410218669055 |
| 22 | 962630898723772565760 |
[1,1,2,6,24,119,708,4914,38976,347765,3447712, 37598286,447294144,5764747515,80011430240, 1189835682714,18873422539776,318085061976105, 5676223254661760,106919460527212950, 2119973556022047744,44136046410218669055, 962630898723772565760] |