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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 26 |
| 4 | 194 |
| 5 | 1581 |
| 6 | 13625 |
| 7 | 122120 |
| 8 | 1126780 |
| 9 | 10631460 |
| 10 | 102104845 |
| 11 | 994855179 |
| 12 | 9809872626 |
| 13 | 97710157154 |
| 14 | 981636609906 |
| 15 | 9935473707279 |
| 16 | 101214412755647 |
| 17 | 1036991125300748 |
| 18 | 10678412226507032 |
| 19 | 110459290208905008 |
| 20 | 1147261657267290037 |
[1,1,4,26,194,1581,13625,122120,1126780,10631460, 102104845,994855179,9809872626,97710157154, 981636609906,9935473707279,101214412755647, 1036991125300748,10678412226507032, 110459290208905008,1147261657267290037] |