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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 57 |
| 3 | 505 |
| 4 | 4089 |
| 5 | 32761 |
| 6 | 262137 |
| 7 | 2097145 |
| 8 | 16777209 |
| 9 | 134217721 |
| 10 | 1073741817 |
| 11 | 8589934585 |
| 12 | 68719476729 |
| 13 | 549755813881 |
| 14 | 4398046511097 |
| 15 | 35184372088825 |
| 16 | 281474976710649 |
| 17 | 2251799813685241 |
| 18 | 18014398509481977 |
| 19 | 144115188075855865 |
[1,57,505,4089,32761,262137,2097145,16777209, 134217721,1073741817,8589934585,68719476729, 549755813881,4398046511097,35184372088825, 281474976710649,2251799813685241, 18014398509481977,144115188075855865] |