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| n | a(n) |
|---|---|
| 1 | 81 |
| 2 | 487 |
| 3 | 2581 |
| 4 | 12373 |
| 5 | 55929 |
| 6 | 241933 |
| 7 | 1015889 |
| 8 | 4174941 |
| 9 | 16895401 |
| 10 | 67647573 |
| 11 | 268781649 |
| 12 | 1062687069 |
| 13 | 4187377529 |
| 14 | 16469997477 |
| 15 | 64715520737 |
| 16 | 254249916141 |
| 17 | 999126102153 |
| 18 | 3928936941941 |
| 19 | 15463007464305 |
| 20 | 60919637465405 |
[81,487,2581,12373,55929,241933,1015889,4174941, 16895401,67647573,268781649,1062687069,4187377529, 16469997477,64715520737,254249916141,999126102153, 3928936941941,15463007464305,60919637465405] |