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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 22 |
| 3 | 77 |
| 4 | 1255 |
| 5 | 2012558 |
| 6 | 2679689 |
| 7 | 9289091 |
| 8 | 18004327 |
| 9 | 38887673 |
| 10 | 56634173 |
| 11 | 72533807 |
| 12 | 82010177 |
| 13 | 104651419 |
| 14 | 2056148051 |
| 15 | 2552338241 |
| 16 | 20390982757 |
| 17 | 27517052599 |
| 18 | 118159068427 |
| 19 | 749474411781 |
| 20 | 5134205287973 |
| 21 | 18028182516671 |
[15,22,77,1255,2012558,2679689,9289091,18004327, 38887673,56634173,72533807,82010177,104651419, 2056148051,2552338241,20390982757,27517052599, 118159068427,749474411781,5134205287973, 18028182516671] |