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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 5 |
| 3 | 11 |
| 4 | 31 |
| 5 | 129 |
| 6 | 731 |
| 7 | 5053 |
| 8 | 40335 |
| 9 | 362897 |
| 10 | 3628819 |
| 11 | 39916821 |
| 12 | 479001623 |
| 13 | 6227020825 |
| 14 | 87178291227 |
| 15 | 1307674368029 |
| 16 | 20922789888031 |
| 17 | 355687428096033 |
| 18 | 6402373705728035 |
| 19 | 121645100408832037 |
| 20 | 2432902008176640039 |
[2,5,11,31,129,731,5053,40335,362897,3628819, 39916821,479001623,6227020825,87178291227, 1307674368029,20922789888031,355687428096033, 6402373705728035,121645100408832037, 2432902008176640039] |