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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 15 |
| 4 | 173 |
| 5 | 1815 |
| 6 | 18172 |
| 7 | 177072 |
| 8 | 1695717 |
| 9 | 16046799 |
| 10 | 150557876 |
| 11 | 1403583192 |
| 12 | 13020620912 |
| 13 | 120319453072 |
| 14 | 1108357767441 |
| 15 | 10183814123055 |
| 16 | 93371810974677 |
| 17 | 854560447928127 |
| 18 | 7809223022293132 |
| 19 | 71269611577048224 |
| 20 | 649693587382657728 |
[0,1,15,173,1815,18172,177072,1695717,16046799, 150557876,1403583192,13020620912,120319453072, 1108357767441,10183814123055,93371810974677, 854560447928127,7809223022293132, 71269611577048224,649693587382657728] |