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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 8 |
| 4 | 28 |
| 5 | 125 |
| 6 | 731 |
| 7 | 5052 |
| 8 | 40352 |
| 9 | 362917 |
| 10 | 3628935 |
| 11 | 39916936 |
| 12 | 479002360 |
| 13 | 6227021561 |
| 14 | 87178296283 |
| 15 | 1307674373184 |
| 16 | 20922789928484 |
| 17 | 355687428136485 |
| 18 | 6402373706091651 |
| 19 | 121645100409195652 |
| 20 | 2432902008180269688 |
| 21 | 51090942171713074013 |
| 22 | 1124000727777647602015 |
[1,3,8,28,125,731,5052,40352,362917,3628935, 39916936,479002360,6227021561,87178296283, 1307674373184,20922789928484,355687428136485, 6402373706091651,121645100409195652, 2432902008180269688,51090942171713074013, 1124000727777647602015] |