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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | -1 |
| 2 | 0 |
| 3 | 4 |
| 4 | 22 |
| 5 | 118 |
| 6 | 718 |
| 7 | 5038 |
| 8 | 40318 |
| 9 | 362878 |
| 10 | 3628798 |
| 11 | 39916798 |
| 12 | 479001598 |
| 13 | 6227020798 |
| 14 | 87178291198 |
| 15 | 1307674367998 |
| 16 | 20922789887998 |
| 17 | 355687428095998 |
| 18 | 6402373705727998 |
| 19 | 121645100408831998 |
| 20 | 2432902008176639998 |
| 21 | 51090942171709439998 |
| 22 | 1124000727777607679998 |
[-1,-1,0,4,22,118,718,5038,40318,362878,3628798, 39916798,479001598,6227020798,87178291198, 1307674367998,20922789887998,355687428095998, 6402373705727998,121645100408831998, 2432902008176639998,51090942171709439998, 1124000727777607679998] |