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| n | a(n) |
|---|---|
| 1 | 15 |
| 2 | 87 |
| 3 | 705 |
| 4 | 4350 |
| 5 | 26006 |
| 6 | 156964 |
| 7 | 939006 |
| 8 | 5466749 |
| 9 | 30837420 |
| 10 | 168947111 |
| 11 | 901097968 |
| 12 | 4680202369 |
| 13 | 23651533225 |
| 14 | 116192356397 |
| 15 | 554663937245 |
| 16 | 2572846819549 |
| 17 | 11600123422679 |
| 18 | 50863765123285 |
| 19 | 217051630988778 |
| 20 | 902189285684499 |
[15,87,705,4350,26006,156964,939006,5466749, 30837420,168947111,901097968,4680202369, 23651533225,116192356397,554663937245, 2572846819549,11600123422679,50863765123285, 217051630988778,902189285684499] |