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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 17 |
| 5 | 121 |
| 6 | 891 |
| 7 | 7155 |
| 8 | 63351 |
| 9 | 617463 |
| 10 | 6590727 |
| 11 | 76589127 |
| 12 | 963486567 |
| 13 | 13052781927 |
| 14 | 189537379047 |
| 15 | 2937560365287 |
| 16 | 48409889869287 |
| 17 | 845393769958887 |
| 18 | 15596602532173287 |
| 19 | 303139660882458087 |
| 20 | 6191620542649779687 |
[0,0,0,2,17,121,891,7155,63351,617463,6590727, 76589127,963486567,13052781927,189537379047, 2937560365287,48409889869287,845393769958887, 15596602532173287,303139660882458087, 6191620542649779687] |