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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 66 |
| 3 | 515 |
| 4 | 4100 |
| 5 | 32773 |
| 6 | 262150 |
| 7 | 2097159 |
| 8 | 16777224 |
| 9 | 134217737 |
| 10 | 1073741834 |
| 11 | 8589934603 |
| 12 | 68719476748 |
| 13 | 549755813901 |
| 14 | 4398046511118 |
| 15 | 35184372088847 |
| 16 | 281474976710672 |
| 17 | 2251799813685265 |
| 18 | 18014398509482002 |
| 19 | 144115188075855891 |
| 20 | 1152921504606846996 |
[1,9,66,515,4100,32773,262150,2097159,16777224, 134217737,1073741834,8589934603,68719476748, 549755813901,4398046511118,35184372088847, 281474976710672,2251799813685265, 18014398509482002,144115188075855891, 1152921504606846996] |