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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 9 |
| 2 | 53 |
| 3 | 351 |
| 4 | 2417 |
| 5 | 16839 |
| 6 | 117713 |
| 7 | 823671 |
| 8 | 5765057 |
| 9 | 40354119 |
| 10 | 282476273 |
| 11 | 1977328791 |
| 12 | 13841291297 |
| 13 | 96889018599 |
| 14 | 678223089233 |
| 15 | 4747561542711 |
| 16 | 33232930635137 |
| 17 | 232630514118279 |
| 18 | 1628413598172593 |
| 19 | 11398895185897431 |
[2,9,53,351,2417,16839,117713,823671,5765057, 40354119,282476273,1977328791,13841291297, 96889018599,678223089233,4747561542711, 33232930635137,232630514118279,1628413598172593, 11398895185897431] |