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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 11 |
| 4 | 48 |
| 5 | 349 |
| 6 | 2640 |
| 7 | 23673 |
| 8 | 231504 |
| 9 | 2693241 |
| 10 | 33313680 |
| 11 | 446104845 |
| 12 | 6572693160 |
| 13 | 103319528805 |
| 14 | 1750718151000 |
| 15 | 31865325610545 |
| 16 | 607019625223200 |
| 17 | 12253084499034225 |
| 18 | 263721891513921120 |
| 19 | 5900460781451357205 |
| 20 | 139338570648068278200 |
[1,1,2,11,48,349,2640,23673,231504,2693241, 33313680,446104845,6572693160,103319528805, 1750718151000,31865325610545,607019625223200, 12253084499034225,263721891513921120, 5900460781451357205,139338570648068278200] |