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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 217 |
| 3 | 2190 |
| 4 | 19981 |
| 5 | 170898 |
| 6 | 1398097 |
| 7 | 11075670 |
| 8 | 85654261 |
| 9 | 650280378 |
| 10 | 4865931577 |
| 11 | 35994162750 |
| 12 | 263799130141 |
| 13 | 1918854559458 |
| 14 | 13871649322657 |
| 15 | 99770067275430 |
| 16 | 714554190919621 |
| 17 | 5099624595840138 |
| 18 | 36287658424563337 |
| 19 | 257574399980365710 |
| 20 | 1824480913344734701 |
| 21 | 12900603911464394418 |
[1,18,217,2190,19981,170898,1398097,11075670, 85654261,650280378,4865931577,35994162750, 263799130141,1918854559458,13871649322657, 99770067275430,714554190919621,5099624595840138, 36287658424563337,257574399980365710, 1824480913344734701,12900603911464394418] |